Disclaimer: This is from a player's perspective in adventure 6, so I do not know about the obscurer aspects of ZEITGEIST lore.
First, the good news: Regarding classes, Anything goes. Well, almost.
Second, some classes are more common in regions other than Risur, so you may want to consider this.
- Native Risuri tend towards martial and nature-based classes with the occasional arcane student.
- Crisillyiri favor divine classes and anything "occult" might be shunned (though I can definitely see them taking value in scholary wizards).
- Ber has lots of martial and primal folk with the occasional sorcerer (draconic bloodline), but they really dislike enchantment magic and don't have a strong scholastic tradition yet.
- Danor is a special case: They don't have magic. Period. So they usually stick to martial and tech classes with the rare outliers being noble/wealthy Danorans who study magic abroad and have enough money to import magic items.
- I don't have too much info on Drakr, but considering their history, these guys would favor tech, martial and arcane classes, even with its more occult aspects (like demonology)
This being said, let's have a closer look at the classes:
Barbarians might be hard to integrate into the RHC and I guess it is easiest to play a Totem Warrior or Ancestral Guardian stemming from Ber. Or you could play a Berserker who's a bit like the Hulk or Jekyll/Hyde. Storm Heralds could have links to Storm Fey, who are a thing in Risur.
Bards are a very easy fit. First, you have the Dockers and I'm pretty sure Rock Rackus is a glamour bard. A Lore bard could be a graduate from Pardwright. And Valor bards make excellent squad leaders while Swords bards are very swashbuckler-y, so definitely a natural fit for the setting. There is also the elfaivaran warrior-poet tradition if you wish to go there.
Clerics are tougher. As I said before, most Clerics would come from Crisillyir and be part of the Clergy, serving as priests, Godhands or hierarchs. Also, besides Triegenes, Srasama (who is dead and usually doesn't grant spells) and the god who turned into a Rakhshasa and got killed by Dhebisu there are no named gods, so prepare for some serious work if you don't go the Crisillyiri route and wish to play a Cleric in the traditional sense. That being said, unusual constellations do work, such as our Old Faith cleric.
Druids and Rangers are both a natural fit for risuri traditionalists. Circle of Dreams and Circle of the Moon work pretty well (even if there are no lycanthropes in Risur) as the Dreaming is directly linked to the Moon, Av. Land druids work as well. Twilight Druids could be Spirit Mediums. Shepherd might need some tweaking due to the summoning limits (though I don't know whether they'd apply to creatures summoned from the Dreaming).
Ranger subclasses are almost all applicabe, but Horizon Walkers don't make that much sense as planar travel, summoning and extraplanar presence is really limited. Primeval Guardians are excellent for someone who's interested in a more mystical (possibly fey-oriented) approach.
Fighters and Rogues are both natural fits for RHC agents, with fighters being more combat-oriented and rogues being more sneaky agent style. Both classes' subclasses are versatile enough to perfectly fit in, even if they don't have that *special something*. So you may wish to pair them with an interesting Theme feat - Yerasol Veteran is pretty straightforward, but anything goes.
Monk, oh Monk. I don't know of any monastic traditions in the setting, but some philosophical schools in Drakr might have turned to martial practices. You can always tweak the class' background, but this needs work.
Paladins, again, very likely to stem from Crisillyir and very likely Godhands or ex-Godhands. Oath of the Ancients could be perfect for an Elfaivari disciple of Vekesh though with its fey/nature-like themes.
Sorcerers can come from everywhere and might find refuge in Risur or have very personal reasons to join the RHC (they are always in need of mages). Draconic sorcerers may have ties to Ber and be descendants of the Dragon tyrants. Giants live in Ber, even if they lack the distinct background. Divine sorcereres work extremely well as Devas (see my entry about gods) as they carry their divine spark within. Phoenix sorcerers are a bit tricky (I don't know of any phoenixes), but their powers are great for a Vekeshi Mystic. Storm magic is known in Risur and there are storm and sea fey. Last but not least, the wild mage could be born in the wild magic areas of the Malice Lands.
Warlock. Archfey. Nuff said. No, seriously, a risuri Warlock with ties to the Unseen Court is a great opportunity to hook up with the setting. Fiend and celestial are both hard to do in a traditional sense (one could always go Deva or Tiefling though). Great Old One could work with a fey Titan and Hexblade is pretty much universal.
Wizards are a pretty much universal class for a Risuri, so anything goes as well. Bear in mind that there are academies, so magical students might not be that rare. Being analytical academics, they'll have an easy time integrating into the RHC.
Now I know that there are some 3PP and homebrew classes out there and I surely don't know all of them. But two classes that would definitely fit the ZEITGEIST setting would be Alchemist and Tinker. Add in something fey-related (like the Feywalker) if you like.
