Switch skin option?

Hey guys, I thought it could be really cool to add an option for switching skins. Suppose you buy Gentleman Cho'gath 1820. Then after a while you want to use another Cho skin, but why would you pay for an entirely new skin because then you will waste the 1820 you spent. So what if we could pay a smaller amount of RP for a skin switch? Let's say the cst of a skin switch was 400RP. So if I want Prehistoric Cho'gath 750, I pay 400RP and get refunded 1820-750 = 1070RP. If I then want Gentleman Cho'gath again, I have to pay the 1070RP + another 400.

Good idea?