I would just like to make a statement here:
Basically I have looked over your thoughts and I think that they have merit in theory, however at this point in the game they may be too late. The best three characters are the best three for their overall playstyle and ability to control the match, the nerfs that they have recieved, and the buffs that the other characters have received may not be enough to bring anymore balance. Looking over these changes and with my own experience on the programming side of Brawl+ for the last 8 months I still see the top three characters dominating the game almost entirely.
MK has the best spacing, has actual combos during hitstun, the best recovery in the game and he kills low. By removing some of his kill power he still dominates the stage for the entire game and all you will be doing is making him more campy as his spacing game is hard to beat.
Snake's grenades will still take on their insane ability to control the field and weaken most approaches with the sheild while the opponent is approaching. This still allows Snake to take on his great power to control what is happening on stage. Also, dont forget forward tilt with its excellent range, power, and speed.
Wario has a bit weaker of kill moves, but dont forget that he racks damage really well and has great spacing due to his air control.
By making these three characters have less kill options all you are really doing is taking the already 8 minute matches and making them more slow and taking longer (at least in my opinion).
Some of the changes that you have put in I looked over and honestly they just made me laugh. Example: Ganon upB uppercut: Why would you be near the edge in a game with very limited edgeguarding as is? Ganon would just be edgeguarded further out, or not at all. This doesnt really change much with him at all.
Characters like Falcon that got kill move increases or a tripping D tilt or things of that nature really doesnt do much for the game overall. Defense is such a priority in this game that if Falcon was to throw out one of these moves he would just be punished out of a sidestep, roll, AD, or sheild anyhow. It really doesnt appear to change much.
I think the theory behind it is good, but I honestly dont think it will help very much and you will still see the top three dominating more matches, but also taking more time overall for those matches to reach completion.
Props for the effort and props for actually taking the initiative on this, but I personally dont know how well it will actually work out, especially considering the higher ups that played Brawl were initially vehemently against the removal of tripping, and now this is expected to be acceptable?
Good luck to you in all that you do on this project, and again, props to you from me.
Edit: One minor point that I forgot:
By removing things like grab release infinites and the ICers infinite throw to throw, what will these characters have to make them at all viable?
Most characters had grab release infinites on Wario and he is still third best in the game. ICers have only one real trick in this game and thats the throw to throw, you take that out and what do they really have?