I think that removing Meta Knight, Ice Climbers, Olimar, and Diddy Kong would be a terrible idea; just look at past comments on this thread, I'm not explaining myself because I don't know as much as them.I sought a thread to post this in, and now I have found one. Brawl solutions that may or may not work. Warning- some of these theories are very out there, so read with caution. I'll drop a spoiler over it so people can pass it by, cuz it's a lot.
You see, the problem with Brawl is that it was made with four players in mind. Attacks are best for hitting multiple players at once or focusing on racking up damage against one. To avoid a lockdown, you'd need a buddy can bust you out. That's why I think to save Brawl, it should be played in exclusively doubles. That also could potentially break a lot of the stalling patterns seen in the game.
Speaking of stalling, I think the timer should be removed to completely obliterate the purpose of stalling. The reason Brawl died in the first place is that it was a game of hit and run, since it was a lot easier to run than hit, and then wait for time to run out.
Also, I think that by removing Meta Knight, Ice Climbers, Olimar, and Diddy Kong, most other characters become much more capable and actually a lot more balanced. I played mostly mid tier characters in Brawl and they're a lot of fun, despite not being designed for high-level, technical play.
And just look at the amount of stages that could be potentially legalized in a game like this. Battlefield, Final D, Yoshi's Island (new), Smashville, Halberd, Delfino, Castle Siege, Lylat, Frigate Orpheon- heck, even Brinstar and Jungle Japes have a chance, they're 3DS counterpicks at my local and they're pretty popular, especially in doubles. You might even be able to allow walk-offs due to the nature of the gameplay style.
Using this ruleset, Brawl can be the "easy to learn, hard to master" game of patience, accuracy, team chemistry, and doubles strategy rather than a game of intense rushdown combo ability and technical prowess. What do you think?