Why is that really a problem though? That's part of the reason why we wanted soldiers that were more loyal to us than to the province they're from.
I agree that we need more bodies if we want to fend off the attacks, the update makes that clear. However, chariots will also allow us to quickly move soldiers around, deal a ton more damage to them while fighting, and chase them back and hit them where it hurts. If we just want to defend our cities better then yes, [Main] Warriors is objectively superior. If we want to hurt the nomads enough that they stop raiding then [Main] Chariots is the better choice.
And again, unless confirmation otherwise arrives, I think we need to [Main] the Art Patronage if we want that upgrade. It might be a chance if we [Secondary] it, but with [Main] it should be a lot better and give us Prestige (which I suspect might start becoming very important soon with the new mechanics coming)
edit: and considering Academia Nut's not online right now... I don't think that confirmation is coming