Master Hand and crazy hand do not need to be playable... although I did play as Master Hand in Melee using action replay, but of course it locks up the game in the end. It was weird controlling Master Hand, because the same buttons did different things different times. Basically, Master Hand is NOT meant to be a playable character and some people have ridiculous ideas as to who should be playable *cough*Ridley*cough*.
HOWEVER, one thing I would REALLY like to see in SSB4, more than anything, is more subcharacters. You know, like Pokemon Trainer, Samus and Zelda. For example, Link could be Adult Link / Child Link, or even more awesome you could play as Zora Link, Deku Link, etc. but I think the Zoras, Gorons and other Zelda characters could work as characters on their own. Ganondorf needs his moveset totally redone. He needs, more than anything, to have the most famous move he's used in almost every Zelda game (ALttP, OoT, WW) and that is to create this magic orb above his head that shoots at an enemy and then they can of course knock it back at Ganondorf and he can knock it back at them, just have some good old Zelda vs. Ganondorf fights, except with anyone vs. Ganondorf. Also, make it random to where once in awhile it create alot of little magic balls instead (again, ala OoT, etc.) Why they made Ganondorf's moved based of Captain Falcon's in the first place is beyond me. Also, Pikachu could have sub characters like Pichu (why not?) and Raichu. Sub characters would be unlockable.
I would never recommend getting rid of old characters. People always want more and more characters, so why get rid of old ones? That just means less characters. Actually, there is one case in which I would recommend getting rid of old ones: to make room for more, better characters.
And yes, the stage builder needs more to it. Like, the ability to flip objects vertically or 90 degrees; and select what type of stage it is, like brawl, target smash, multi-man brawl, adventure, whatever. Maybe not everything, but at least brawl and target smash. But of course, if they could manage to do everything, that would be fantastic.
It's funny, Sakurai acts like Brawl is the epitome of Smash Bros. You know what, Sakurai? You did a good job with brawl, it's a great game, but if you didn't have anything to do with the next Smash Bros, I would be just fine with that. Maybe then we could actually get an online leaderboard. Odd, isn't it? The most competitive Nintendo game lacks an online leaderboard whereas Metroid for the DS has a leaderboard (or at least it did, I haven't checked since I played the game last, which was shortly after I bought it). Oh, well, if Sakurai didn't work on it, we wouldn't have had Snake, so that's good.
I'm sure alot of people here know already, but Iwata, currently Nintendo's president, originally programmed Smash Bros 64 himself, so that why I believe Nintendo can make another Smash just fine without Sakruai's help. In fact, I don't want him to work on the next Smash Bros. game. He can go work on his xbox project now. (Master chief versus... wait, what other mascots are on xbox?)