Chubby What @UnseenMind suggested is actually very easy to implement in code. I liked your idea, but I like the one above too because it guarantees you continue to get cookies if you keep playing - which is like the good old days before they changed it. This way you still feel like you're building up your cookies that you can later spend.
Before they changed it I managed to save around 250K cookies. That was great because I can now easily buy any outfit I like if I see it in the shop and it only requires cookies to pay for it.
Just my thoughts, but I like the suggestion. We may be able to all work together to refine it (may not be required), but it seems pretty strong to me and should be easy to do.