New idea for usage of left over rp

Every time me or my friends purchase rp we always seem to have some leftover rp that we could make no use of, wouldn't it be a cool idea to have a rp to ip calculator which converts rp to ip, which will mainly be used to convert leftover rp to ip. But this calculator would have the same ratios to the cost in champions like the ratio of 975 rp to 6300 ip or lower because if it were higher players could get champions for cheaper rp prices after converting rp to ip and purchasing the champion.