I think I would be content with Super Smash Bros. for Nintendo Switch if it includes:
PLAYABLE CHARACTERS
- all playable characters from SSB4, including the DLC fighters
- all the cut veterans from Melee and Brawl
- a few more newcomers such as Alph (semi-clone of Olimar), Inklings, and Simon Belmont
STAGES
- all the stages from SSB4 Wii U and SSB4 3DS, including the DLC stages
- all the cut stages from Smash 64, Melee, and Brawl
- a few more new stages (a Splatoon stage maybe?)
NON-PLAYABLE CHARACTERS
- all the Assist Trophies from SSB4
- all the cut Assist Trophies from Brawl, including Little Mac (appears when he's not in the match)
- a few more new Assist Trophies such as Spring Man from Arms
- all the Pokemon from SSB4
- all the Pokemon from Smash 64, Melee, and Brawl, including Charizard (appears when he's not in the match)
- a few more new Pokemon from Sun & Moon, including Alolan Meowth (based on Smash 64 Meowth)
COSTUMES
- all the recolors from SSB4
- all the cut recolors from Smash 64, Melee, and Brawl
- all the Mii costumes from SSB4, including the DLC costumes
- many more new Mii costumes (Chun Li costume, maybe?)
Oh, and being able to play Smash Run on TV.
Not saying it will happen... but it's nice to dream.