I'd say that would make the game devolve into a hose feed-spam game, because you already use credits to upgrade your money output for your restaurant. It'd quickly ramp up both currencies and remove any challenge because you could just buy all the credits you need in every following town.
You're right, the game is very easy at the moment. I've been thinking about this and what I could do to add some challenge for players who'd like that & also make it feel a bit more realistic.
I plan to add difficulty options, set when starting a new game & changeable at any time in settings. The current version would become the new easy mode. Medium and hard would add more pushback from girls, a new dieting system and the possibility that they get upset with you if you go too hard with the feeding.