When you build a campaign setting, take a moment to sort out which classes occur in which societies, and what function they typically have therein.
Allow me to explain: classes tend to be of two types. Some correspond to a general profession (e.g. the general conception of a Fighter, who might be any sort of warrior), while others to a specific one (e.g. a Bladedancer, who is specifically a priestess of Ianna and member of the Temple of Blade and Veil). I posit that the second type is generally better, from a simulationist standpoint. Being called a “Fighter” in-world suggests little; being a “Bladedancer” suggests much. The names we use for things matter, and when they can be used in-character they make the world all the richer.
First, consider how the Bladedancer class encodes information about the setting. Ianna’s priesthood is twofold: Bladedancers make up the militant wing, while Priestesses the civic wing. They are not like the Clerics of Ammonar - not in equipment, tactics, or even spells, and there is no such thing as a “Cleric of Ianna.” Ianna as Goddess of Love and War of the Auran Empire is served by lightly armored skirmishers whose spells let them become angels of death; she has no heavy infantry to drag out a war, but driven by passion will strike swiftly. These sorts of mechanical distinctions reflect the real differences within the setting in an essentially simulationist fashion, and communicate this clearly and precisely via mechanics (which also happens to be one of the most certain ways to encourage players to understand that lore - and to want to do so).
Lacking those mechanical differences, a perspective that takes the implications of mechanics on the setting seriously would be forced to conclude that the priesthoods of various deities are essentially similar. (And indeed, if that were an accurate assessment of the setting, those mechanical differences should not exist.)
Second, consider how classes bestowing membership in discrete organizations naturally ties characters to the world. If playing a Mage means being a member of the Tower of Knowledge, and of a College within that aligned to a specific variety of magery, then any Mage created now has concrete connections. They have a Master they study under to learn spells, a group of natural allies, a code of behavior expected of a Magister of the Tower (and attendant social station), etc. The same naturally extends to priests within their faith, and sometimes to thieves within their guild.
Third, as a worldbuilding tool, this pushes the Judge to flesh out those organizations that PCs will naturally be a part of, which tends to add valuable structure to the otherwise blank canvas that comes with building out the NPCs of a realm (both in terms of knowing what to do, and focusing on those things most likely to be relevant in play).
Were we to apply this standard to the Fighter, we might naturally conclude that “Fighter” actually means “someone who served in the legions,” thus explaining why commoners and noblemen alike hold that same class, and likewise both cavalry and infantry - they are essentially similar, and any actual differences between them can be handled at the level of their proficiency choices. That has cool implications of its own and synergizes very neatly with the Template system, both at the level of indicating function within the legion (Riding => cavalry, Tracking => scout, Signalling => messenger, etc.), and perhaps as well that different legions have different specialties (Fighting Style [two-handed weapons] might suggest former membership in Legion VIII Comprimens).
Some may look at the above and be concerned that a level 1 Fighter doesn’t need that much backstory. But that’s just the thing: this backstory is the abduction of their mechanical choices, and is trivially determined if and when it becomes necessary. Indeed, it largely obviates the need for the player to compose any backstory, by tying it implicitly to their mechanical choices.
Moreover, to elaborate the second point above, it is implied that such a Fighter knows people in Legion VIII, and probably gains a reaction bonus there (and perhaps a penalty with their rivals in Legion IX). Since he is no longer a member, he has presumably earned his citizenship with the accompanying rights and duties. Likewise, I might never have fleshed out the various legions, except that my players who run Fighters will need that information (in similar manner to how many D&D pantheons owe their existence to the players of clerics). And it becomes a worldbuilding tool of its own now: if a gang of brigands are encountered that are all Fighters, they must be deserters, or mercenary auxiliaries, or the corrupt local garrison.
At a setting level, one consequence of this is that it embraces and mechanically represents the significant differences between cultures. Soldiers in town are Fighters because they’ve served in the legions, but the hill-folk have Barbarians who’ve grown up raiding (and just as proficiencies might distinguish Fighters from different legions, they might also designate Barbarians from different tribes). The Priests and Clerics of civilization stand opposed to the tribal Shamans and folk Witches; the Loremasters of the Magisterium rivals to the Elementalists of the Sorcerous Spire and the Occultists of the Prophet of Death.
Two brief mechanical suggestions to reinforce this and add further depth: first, only allow players to play PCs from the starting area of the campaign, or places their prior PCs have visited in the course of the campaign. Second, grant a bonus to reactions with people of “their sort” (served in the same legion, priests of the same god, foreigners from the same place, etc.), and a penalty with their natural rivals.
This works to create a sense of locality, and to make players aware of (and care about) the differences discussed above. Visiting somewhere new to see the world opens up new options for them; vice versa, foreigners from distant lands don’t usually just pop out of nowhere. The established campaign milieu is reinforced, and indeed, it’s good to be a part of it - being a priest of the most important god yields valuable connections, while a shaman of the hill folk has few friends within civilization, and thus PC demographics come to reflect the setting. Instead of wanting to be unique and special, people recognize the value of knowing one’s role in society and playing it to the hilt, a more historically consistent approach. And if someone truly does want to be the outsider, they get treated like an outsider, and get the real experience (as opposed to a milksop’s half-drow/half-tiefling OC that broods in the corner but gets served the same as everyone else).
To deal with a few obvious criticisms.
First, it is easily argued that this makes the ruleset more setting-specific and less able to handle a broad variety of settings without needing adjustment. This critique is accurate but misguided, for this very fact is to our benefit. If things are different, then the mechanics thereof should be different as well; this is a fundamental principle of simulationism, that ensures the mechanics of the setting reflect its reality. If the setting is highly divergent, this can make more work for the Judge - though compared to building an entire world, hardly that much more - but even then, it is work the Judge has chosen themselves in attempting to run such a setting.
Second, some might complain that this makes it harder for players, because they have to learn more classes and more rules. Again, this is basically true, but I do not see it as particularly problematic. My standards for what sort of game I run are high, and I have high standards for my players as well. I am proud to say they generally look at new classes with some eagerness, to figure them out and learn something new, as is right and proper. And compared to including all the classes without curation, this in fact substantially simplifies the number of options to consider.
Last comes the concern of a player who wants to be someone unusual. The barbarian child raised by a legionnaire, or the foreigner from distant lands new come to this one. But I think these are not made impossible by the above, and indeed, are better served by it. A barbarian child raised by a legionnaire is easily modelled as a Fighter, who spends his proficiencies on barbarian talents for which he has a natural aptitude. Many distinctions of this type can be made in this method — providing some measure of individuation is after all a key purpose of the proficiency system in the first place.
NPCs will generally be from the region in which they live, but if a PC wants to hail from a far-off land, he is encouraged to first go visit that distant land as a precursor character, and indeed upon his arrival there he will be a true foreigner as he wished. If he then brings on henchmen there, or dies otherwise, he can begin play in the classes of that region, and their distance from home will be a known fact and not a distant suggestion of the Judge. If he is unwilling to go so far, how is his character supposed to have made the journey? If he persists, perhaps his parents or grandparents made the journey before his time, and he too can spend a proficiency representing that aptitude.
On the whole then, I have found that keying specific classes to specific regions, and curating the list of available classes in general, creates those regional divides meaningfully in the setting. In play, it does so mechanically, through simple adjustments that nonetheless impact players significantly, and encourage them to interact with the setting, tying them into it efficiently and giving them sensible connections in the game world. And even before the game, it gives Judges a framework to work out the influential characters and organizations that players will want to connect with. This aligns the milieu of gameplay with the setting envisioned, adds a realistic and interesting bit of nuance to social interactions, and gives players more things to care about in the world. Sounds good to me.
Well said. There has been a shift in the design of TTRPGs and their video game brethren towards characters and character classes that are disembodied archetypes or lesser forms thereof. I distinctly remember the first time reading AD&D about how the Assassin class would necessarily belong to a guild and be part of a pre-existing association with its own history and goals. The crystallization of these ideas, embedded in that example, inspired the class design in BMD: roles in a specific factional entity.