I feel like this would be a pretty decent idea, it's much like the trading down of badges in wrath and it lets people who have pretty much everything they need from Valor points buy the things they want to buy for leveling alts or just random fun.
I thought of this about 10 minutes ago and I'm sure I'm not the only one that has thought it of but it seems pretty solid and it could be extremely beneficial for the people who're getting bored with their level 85 that sits in a major city when they're not raiding.