0 - Level?
 

Is it possible to do a 0-Level class? I'm wanting to set up so that the races are separate from the culture (not entirely, but with modifications to racial proficiencies.)

Or do I have to do it as a list of subtypes?

I think I would approach this as alternate racial traits. Like if you wanted to have a group of desert elves that train with a short bow and scimitar, have the alternate racial trait replace the normal long sword/longbow with the alternate weapons. You could do this with any racial traits you'd wish.

I'll second this, since the description given for swapping out proficiencies already has lots of precedent in ARTs already (see the Eastern Weapon Mastery ART for elves, for example).