I actually like that you can obtain all the girls without shelling out.
I'd say the most egregious thing is that collect all costs real cash. Maybe create a thing you can buy which autocollects for you for a certain amount of time (1 day/7 day, etc.) for cash, but every collect all costing cash is insane and not even remotely worth it (I also accidentally clicked it and lost koban or whatever they're called =_=).
That said, I won't be able to use any real cash anyways because Nutaku doesn't accept Paypal/Visa anymore. I guess they think I've already given them enough money :^)