Wizard spellbooks don't actually have to be books (they were not in Dark Sun, where both reading and wizardry were illegal for the common person). Any sort of pattern can store information - it could be formed by letters or runes, but also colors, shapes, notches on a hard surface, knots tied into rope, or just about any kind of set of permanent marks. That's assuming a literal thing that you "read" to prepare spells, but the class feature could just be dependant on some kind of fetish that gives the primitive wizard "special powers."
Armor is a bit trickier. You could call the existing armor different things (plate armor becomes brontosaurus hide or something), which is really easy. You could also give bonuses to heavy-armor classes that only apply when they're wearing armor, but you have to balance that against the fact that they're getting their dex or int mod to AC as well (since they're wearing light armor). Probably not a difficult task, but it would require some thought. Or you could abolish worn armor entirely and give everyone a bonus based on class role, maybe.
Armor is a bit trickier. You could call the existing armor different things (plate armor becomes brontosaurus hide or something), which is really easy. You could also give bonuses to heavy-armor classes that only apply when they're wearing armor, but you have to balance that against the fact that they're getting their dex or int mod to AC as well (since they're wearing light armor). Probably not a difficult task, but it would require some thought. Or you could abolish worn armor entirely and give everyone a bonus based on class role, maybe.
