Virtua Fighter characters aren't nearly as Iconic as Ryu is. There's no one other then a 2nd Sonic rep from Sega that truly feels they have an iconic spot amongst the Roster.
And saying it has to be from a different franchises is just making up unwritten rules of which Ryu has already broken two of. (1. 3rd Parties being DLC in general. 2. That there can only be one per company). As I've said many times before, who's to say they can't make the exception even if that is a rule and/or who's to say that's a rule in the first place.
Ryu breaks new ground for potential DLC no matter how you look at it. No one would of even considered Ryu a year ago or even six months ago based on certain unwritten 3rd Party rules. Yet here he is now.
Other sega franchises that could be considered beyond sonic/virtua fighter:
1) Alex Kidd: guy was the mascot before Sonic. Credit where it's due to the mega drive.
2) Toejam and Earl: only possible if ice climbers work.
3) Flicky: you don't have sonic without him.
4) G or the squeaky voiced flying mini zombie that 'killed' G in House of the Dead 2: house of the dead is one of the most popular arcade games ever and has quite the story over the years. And any of the pc's just use guns. I guess you could be G (who's playable in the first, third, and 'overkill' installments) and use an assortment of 'mutant' summons.
5) NiGHTS into Dreams: he looks iconic, he's only had two games, but he's in current sega crossover titles (as is tails) and is beloved.
6) Vyse: he went from sega to Nintendo easily, I love his game, I love his design down to the eyepatch/monocle, and he's in crossover games now. Plus the Arcadia series overall was pretty great.
7) someone from the phantasy star series: we all want phantasy star online 2 on wii u. Why not?
8) billy hatcher: does not really belong on this list. Nice design and fun game though.
9) kid chameleon: see billy hatcher
10) the prince from the Oasis series: beyond oasis is the genesis answer to 'a link to the past'. Don't believe me? Go download it on the wii virtual console. I'll see you two days later because all you've done over those two days is play that game.
11) shinobi from shinobi: shinobi.
12) streets of rage: get the roller skate kid.