Not Refunds, Buybacks
This is partly complete whinery, but also just an idea I like.
I didn't even know that there were refunds available. I never thought about getting rid of skins or champions until the Pool Party bundle came out and I bought it. It was then that I realized that I have way too many skins for Renekton (a compliment on the awesome designs he's been given).
But then I thought more about it. There are champions that I have skins for that I don't even play anymore. Not because I don't like the champion, but because you, Riot, changed them and made them something I don't like. Lil' Slugger Trundle, for example. I loved Trundle before even though I knew he wasn't the strongest. After the visual upgrade, though, I hate that skin and I don't want it anymore. I believe I might have two Shaco skins from back when Shaco was a viable champion. I didn't change, he did, and I don't like it.
However, I can't get refunds for those skins because I bought them years ago. Instead, I'd love to see a buyback system. Maybe 50% of the original RP spent on the skin, or even 50% of the current price. I don't care, just some way to recoup some of the money that wasn't a waste at the time, but is now through no fault of my own.
Admittedly, the Renekton skin-gathering is my obsession with the champion (even before he was cool!), but I see no harm in allowing us to recover some of the money we've spent and use it on other skins instead. I'm also cool with this not being available for champions, because it's a better idea to hang on to them, anyway.
TLDR: 50% RP return rate for unwanted skins.