I think giving each character their own home stage would be a good idea. We have so many good stages from the past three smashes we don't have to have a massive amount of new stages especially when each version will have their own exclusive stages. Heres an idea of how it could work:
(Wii U/3DS)
Mario

elfino Plaza (Brawl)/3D Land
Luigi: Luigi's Mansion (Brawl)/ LM2 stage
Peach: Princess Peach's Castle (Melee)/Peach's Castle (64)
Bowser: Bullet Train*/ Bowser's Airship*
DK: Jungle Japes (Melee)/ Kongo Jungle (64)
Diddy Kong: DKC:TF stage/DKCR stage
Yoshi: Yoshi's Island (Brawl)/ Yoshi's Island (Melee)
Wario:Wario Ware Inc (Brawl) / Wario Land
Rosalina: Mario Galaxy/Rainbow Road
Link: Skyloft/Great Bay (Melee)
Zelda: Hyrule Temple(Melee)/Sanctuary*
Ganondorf:Bridge of Eldin (Brawl)/Gerudo Valley
Toon Link: Pirate Ship (Brawl)/ Spirit Train
Pit: Skytown (Brawl)/ KI:U stage
Samus: Pyrosphere/Planet Zebes (64)
Kirby: Epic Yarn stage/Canvas Curse stage
King DeDeDe: Green Greens (Melee)/Dreamland (64)
Metaknight: Halberd (Brawl)/ Fountain of Dreams (Melee)
Pikachu: X/Y stage
Pokemon Trainer: Pokemon Stadium 2 (Brawl)/ Pokemon World Cup*
Jigglypuff: Pokefloats (Melee)/ Saffron City (64)
Lucario: Pokemon Colloseum*/Spear Pillar (Brawl)
Marth: Altea/Aero Fierox
Ike: Castle Siege(Brawl)
Ness: Onett(Melee)/Fourside (Melee)
Lucas: New Pork City
Fox: Corneria (Melee)/Sector X(64)
Falco: Lylat Cruise(Brawl)
Wolf: Venom (Melee)
Ice Climbers: Icicle Mountain (Melee)/Summit (Brawl)
Mr. G&W: Flatzone (Melee)/Flatzone 2 (Brawl)
R.O.B.: Consoles/Handhelds
I think you get the general idea. I'm missing a few and this idea doesnt exclude more stages for different franchises outside of their home stage. I put * next to a few stage ideas I had:
Bullet Train could be based off SM3DW's Bullet Trains enemies such as the Koopalings and Kamek could appear in the background sending obstacles such as Cat Bullet Bills.
Bowser's Airship would be a similar thing with Bowser Jr. or Boom Boom/Pom Pom appearing in the background sending out Tanooki Bullet Bills
Sanctuary could be based on ALTTP/ALBW's Sanctuary in the forest with the graveyard nearby.
Pokemon World Tournament would be based on X2/Y2's world tournament where various E4 members, Gym Leaders, Rivals and Champions such as Misty, Cynthia, Brock, Blue, N, etc. could appear in the background and send out their signature poke as a stage hazard similar to the stadiums.
Pokemon Colloseum would just be a Colloseum based on the console games.
An idea for ROB would be his stages would take place on hardware developed by Nintendo. Consoles would be on the Wii U version and Handhelds on the 3DS version.