I'd really like to see some additions to online modes; have a section that makes custom moves playable with strangers and a way to play with amiibos online as well (preferably with friends and going up against strangers' amiibos).
Offline, I'd like to see the stage builder tweaked a bit. Bring back blocks that fall when you walk on them, and allow for placing blocks with buttons along with drawing them. An offline tourney mode would be cool as well, and a few more challenges would be nice.
Character wise, if I could pick anyone, I'd go with Amaterasu from Okami. Almost assuredly won't happen, but...hey, she's been in more games on Nintendo systems than Cloud was. I'd like to see another Metroid character included; perhaps someone like Rundas.
Some new stages would be great too.
