You get, say, one re-roll a month.
No bottom tier icons allowed, only second and prime icons, you can trade one in for another icon at random but it's untradeable.
Think it'd be a good little idea for if you make a bad decision with an untradeable prime or whatever, but it doesn't necessarily kill the market because it's not tradeable and if needs must it could cost 30k or whatever?
A good idea? Just something to increase longevity, and the chance to try out new players in the process.