I think you could add new tiles without the player getting lost in a flood of exotic mechanics. For example, you could have a set/type of levels that have a single additional tile (like a park that needs to have at least 3 houses around it or something you think would work better), and then swap that tile out for other tiles in other sets/types of levels. That way there is depth in that there is variety of mechanics, but they’re not all at the same time so they shouldn’t be overwhelming.
Just an idea! Love the game. :)