Simply as stated: Gold becomes a limited resource, so if you have 50 gold and it takes 50 gold to build Structure-A or Structure-B, now you can only get one.How does that ultimately change anything?
If the design is good, then your choice will have both positive and negative consequences for how it impacts gameplay.
This solves many issues since the current design must understand all structures can be built, so they cannot have effects that are too meaningful. Additionally, territories become more unique since you will have different buildings in different places (or playthroughs).