Hybrid random mode for ARURF/ARAM?

It would be a variation for ARAM and ARURF: the champ pool gets divided into tiers based on their power in those modes. When champ selection begins, a tier is randomly chosen: then, each player can pick any champ he owns from that tier.

This way those modes don't have to be perfectly balanced, yet we'd see less curbstomping, we'd get to choose our champ (though from a limited pool), and we wouldn't see the same champs every game.

(Of course, no rerolls... how would you even use them in this system, btw?)