Honestly if it were my game, I would spend time polishing the existing gameplay before adding new features. I didn't mention it because I believe it goes without saying. Since I'm in college I was able to ask a bunch of classmates to try my game and I tweaked the levels a lot after gauging their reactions. I can't really give you advice on what I would change specifically to make it feel better, you're the one who's spent the most time developing this concept so you will know what would make the game fun.