Sure, it would be a little insane. But how awesome would it be if a champion had spells that varied based on the skin used. It would also be a neat possibility for reforms - classic skin, classic kit.
Some people actually liked old urgot's gameplay. Or Graves. MORDEKAISER...
Not going to happen for a large number of reasons.
A lot of old kits got changed to remove toxic, unbalanced kits from the game (poppy, yorick..), plus locking a champion beyond RP would not be tolerated.
Aside from a few joke skins with 1 damage passives and suck, they need to be kept entirely cosmetic.
So you're proposing a Pay-To-Win skin....
And make the skin only obtainable through loot boxes.
/s
