Oh that sounds nice!
I really like the idea of using them to expand the map! It would give them a real purpose beyond just avoiding getting stuck. The ability to remove buildings with these cards is also an interesting mechanic, especially if it allows for better optimization (we can imagine fertile lands that can’t spawn but are buildable on burned lands only and boost food production on it for example).
I also first though plains & forest was here to replace water tiles that are used only for fishing. Maybe aqueducts can have also a special trait with water tiles ?