My 2 cents about B-banning:
B-banning doesn't make a character terrible. I self-impose a B-ban on my Pit usage because his arrows are unbelievably abusive. Pit isn't that bad off; he already has 4 jumps and gliding, so his Up B is unnecessary half the time, because the opponent already is likely to need to launch him hard enough that he'll hit the boundaries before he can try to recover. Side B can be annoying, but it's mostly with the arrows that it's a real pain. The only thing Pit is missing is the reflecting from Down B. Even then, it's not like you can't dodge projectiles.
Of course, if B-banning is a necessity, it shows there's a problem with the character and doesn't fix the issue. >_>
Anyway, I've posted an idea before that could have been in Brawl and toned down Meta Knight considerably, and balanced other characters a bit as well. Here:
http://www.smashboards.com/showthread.php?p=5287994#post5287994
The basic ideas is that a character would get exhausted by attacking too much, and would have trouble attacking further with enough power behind their attacks to generate as much priority for a while. The cap and individual limits would be to ensure that characters like Meta Knight would lose priority sooner and can lose a higher percentage of priority. Yeah, percentage, to further punish spammy Meta Knights and prevent low priority characters from being hit hard. Attack overuse would also be punished further: an attack would have its PD rate increased based on how many times it's already in the queue.
Most importantly, it would be set up so that only certain characters, spam-happy players, move abusers, or simply dragged-out fight participants would notice the mere existence of priority decay.
So you might be asking: what does this have to do with Meta Knight? Well, we know that Meta Knight has low weight and high fall speed, a combination that would no doubt make Meta Knight's priority so extreme: if he has it, well, we have what we do right now; but if it isn't, it's not too much of a bother to KO him by nailing him with a clean hit. However, what if we make sure he can have a priority edge at the start, so that he can't be harassed then, but then he can easily lose it if he's abusive, leaving him open to harassment if the opponent survives the onslaught? That would be appropriate for a sword user of Meta Knight's character. (And yes, that blasted Mach Tornado would cause Meta Knight's priority decay to rack up fast.)