I'd like it if Rural was the only default basic resource designation.
Others might open up if you have the right origin / civic / AP or what not -- e.g. Mining Guilds would give a Mining World designation that benefits Miners and gives +% TV, and Agricultural Idyll might give something which trades off Food for Amenities from Farmers or gives Food upkeep to all jobs for a minor reduction in other upkeep.
@SirBlackAxe -- I say this in part because the current automation can't handle specialized rural worlds at all. It sets Generator World automatically and then doesn't change it in response to my development efforts, even if I have 9 mining districts and zero generator districts.
Specialist / Urban districts are handled correctly right now. If I make a Civilian Goods specialization, the automatic designation changes to match.
But for rural districts, the code does not care what I build. So for the sake of AI and automation -- which seems to build rural districts of the "wrong" type when it sees an opportunity -- I'd prefer simplicity, which means changing the default to Rural so the automation and AI are not wrong so often.
This would improve my experience as a player, and might make the AIs better as opponents.