champ exchange system (of sorts)

Ok I know there is the 3 full value purchase exchange system of either ip or rp whatever u spent for the champ skin or runes, but I have ...lets say 60ish champs and I don't use all of them but theres some I don't have I want id like to see a way I can exchange whichever champs I'm tired of having for either full or partial ( probly partial because doubt they'd give full value either way) of the ip value of that champ. I don't see too many problems with what I'm suggesting...but idk