Does land really need more general boosts? There are millions more resources produced than consumed each and every day. The only thing which keeps land resources prices up is that people are hoarding for the next big thing to craft. If this next big thing is even more boosts the problem just gets bigger and bigger.

I would rather see land cards as a specialist role when buildings come around, since the other boosts are not available there. Like lets say you want to make "fancy resource X". First you need the building, sure, and normal cards can do that, but it would make sense that the normal rate is rather bad. Sort of, you can do it, but not very proficient. If you put a "fancy resource X specialist card" on your plot it boost production in this specific building significantly.

Now you could argue, that you already pay for the building, why need cards to do it efficiently. Well, cards can be rented, so in a way, you create an ingame job market where you can send your cards. You could argue that happens now but it is very general since only PP matters. This would even be a reasonable way how to include research into landcard crafting, since your specialist cards need to study how to do stuff (would make more sense than a permit to build x buildings lore wise).