I think a cap is needed in 3 and New Vegas simply because if you don't it is possible to max out your stats and become some total immortal badass (a problem I have with modern rpgs). I think the level caps are balanced but I do have to mod 3 and New Vegas to receive less skill points and perks...
So I've been playing a ton of Far Cry 3 lately and it occurred to me that the fighting style in Far Cry 3 (automatic cover, stealth hiding in foliage, melee sneak kills etc) could really suit a Fallout game. I think, in my opinion, it would probably play better than in Skyrims engine.
Just...