Clamps
Warning: Jokes!
Final Smashes are fine, but the problem with them is that they're implemented into the balancing of the characters (for example, Meta-Knight has a bad FS but incredible everything else whereas Sonic has bad to average regular moves but the best FS in the game.)
Implementing game balance into an optional item seems a bit off to me.
Falco's Landmaster is better. And they have no idea how good a character will be until the game comes out and the metagame starts developing.
Besides, Jigglypuff's terrible Final Smash and terrible everything else in Brawl pokes a hole in your theory.