Bring back everyone from Sm4sh, as well as those cut from previous instalments (Pichu and Snake can stay out though). Add another 15-20 characters on top of that and I'll be happy. No more 3rd party characters please, there's plenty of Nintendo characters to choose from.
Additions I'd want include:
- Chibi-Robo
- King K Rool (with Kaptain K Rool costume available)
- Ashley
- An FE character that uses lances/axes rather than swords, or perhaps a mounted character
- Sceptile
- Quagsire