And yes, something like that, although, it should probably be generalized so that it wouldn't need much, or any, modification between different types of nodes.
B. building numerous towns, by PCs, which compete against one another
C. PCs are building a town and adventuring at the same time, possibly solving problems their town runs into
I hope that makes it clearer
Special resources also seemed like an interesting idea, seeing as this is D&D. Things like naturally occurring quintessence or something (I hear 4th ed. D&D has some sort of material that replaces xp costs for item creation??).