Release an Arcade version first. Make some money on it and continually improve the balance BEFORE the vast majority of people that are going to play the game actually get to try it. That way their first impression of it is that of an infinitely more polished product than SFV was at launch.
New art style. Doesn't have to be reminiscent of an old style. Like I always see people wanting SF3 or SFA style art direction to come back and while that would be nice I just don't see that ever happening again. Hell use the RE Engine if you want and gives us whatever the hell that would look like.
SFV's launch roster newcomers were all great in my eyes. They all felt fresh and had unique playstyles while still feeling like they belonged in Street Fighter. If SF6 can repeat that while making sure the most necessary fighting styles are represented day 1 then they'll be off to a good start.
Single player modes need to be a focus from the beginning of the console version. You don't have to reinvent the wheel for this. Team battles, Tag battles (EX3 showed me that this can be a fun mechanic in a SF game), Dramatic Battles, Survival Mode, Arcade Mode with endings, Story mode for the lore lovers, and a World Tour mode if you're feeling frisky.
SFV has some of the best and worst music in the series imo. I hope they cut down on the bad and increase the number of good songs for SF6. If they're feeling really adventurous maybe try making memorable NEW songs for SF2 veterans. Arika did that shit in the 90's for at least Sagat, Guile, Chun-Li, and Ryu so we know it's not impossible.
Online. I'm not sure how you'd improve this due to the p2p nature of fighting games. Would a server based fighter work?
Crack Pipe Smoking Dream Scenario: Next street fighter will have 1 guest character. Someone from SNK. Terry, Ryo, Kyo, or Rock Howard. Use the character to tease and build up hype/interest for the next VS game "Capcom Vs SNK 3". Of course the next KOF would also have a SF character as a guest to build to SVC 2.
