Actually, there was only one season where interest alone could net you ocd 7. Interest rates were patched after that, and fixed at 1% before that.
There has been alot of talk about some additional utility out of OCD levels other than the ridiculous max level cost. See here
Its been an idea thats been passed around, but it is a back burner item for the moment out of necessity, due to the backlog of items already on rex and jascha’s plate.