Since reset stones only have a few uses, like temp vip, stat resets, and allowing non-vip to get to 3rd class. Why not allow reset stones to be used to pay for VIP, say 7 stones for 30 days, 19 stones for 90 days, and 34 for 180 days, since each stone is worth $1 on the cash shop. It'd keep the resets stone valuable since people would buy them to keep their VIP up, plus because the only other way to get them besides the cash shop is from eden medals, they'd keep their value to Warpportal, so they more than likely would not lose money, since 'someone' has to buy the stones, if not using the medals.
Yes I know I'm ripping a concept from another game, but hey, if it works for them, it, in theory, should work for Warpportal.