Your ideas are good, however unoriginal and have been thought up and put out on the forums many times, and i can't speak for anyone else on these forums but me, i understand why you would post this. You have not been here long enough to realize what has been stated and in my eyes is completely understandable.
Now to answer your questions 1. New story, yes but no. As been mentioned before no one really cares enough to rework all of the story. (Which was not much.) 2.New menu. I think yes as it has been done before with the character selection and stage selection. Why it hasn't been i can't tell you. 3.More characters. Is being worked on and can be done at the moment but is buggy and can, not will, corrupt your save file. (I wont get into this one simply b/c there's a big thread on it already) 4.New stages. Done and Done.
i know there is a tutorial and editing hack on the vault, i will find a link
Edit: Well i cant find the link to the tut. or the hack it self. i tried looking in the menu tab but i found nothing. you can look there if you choose, its worth a shot
personaly if you use one minty character you should use minty for the rest (if not most) just to keep it that brawly kinda feel where everyone has the same recolors, not sure if you under stand that
and mabye dark versions for everyone since there is like dark link, dark toon link. just mainly black with red eyes but again, just a thought
why not make fox and falco have there assault constumes? mabye just the textures dont have to be models, idk just an idea. mabye use false character (SSE).