I'm not sure if it's yet been discussed here, but how do you think people would feel about incorporating iconic SF moves from other characters into Ryu's moveset? Obviously being faithful to him should always be the priority, but if you take every move from him out of SFIV at least, you still lack some moves, which, if you look at other characters, can easily be filled with instantly recognisable attacks. For example:
Up Air - Flash Kick (Guile) - This is the big one for me as when trying to come up with a moveset for Ryu, there isn't really anything that I think would make a good Up Air, and this is perfect.
Up Throw - Spinning Piledriver (Zangief) - Obvious kill throw. Ryu's throws really feel most appropriate as Down/Back throws so something needs to be implemented here.
Side Smash - Tiger Knee (Sagat) - This could admittedly be a Forward Air as well, but Ryu has plenty of punches for that, and there are enough parallels between Ryu and Falcon (pretty much the entire set of standard attacks, plus the U-Air if you went for Flash Kick) without giving him a knee as well.
Mostly I am curious as to the reactions if people incorporated other characters moves into Ryu. I can see it being taken both positively as a nice nod to the series as a whole, but also more negatively by people wanting to stay more strict to the games (though I'm not sure how you can).
But then he'd just be ryu inserted into smash
I'd be extremely surprised if we got much more than "Ryu in Smash" - between him being a 3rd party, with the pressure to stay true to his character, and the fact that his moveset is so iconic (I'd argue most famous in fighting game history) the number of people who'd want to change it is a vast minority.
I will happily wager Ryu's moveset is for the vast majority going to feel like a straight translation from Street Fighter. There is a small amount of potential for mixups in some of the moves he doesn't have a direct analog for in Street Fighter (namely Up and Back attacks) but they're almost certainly never going to choose something new where they can put anything even remotely recognisable from Street Fighter. Anyone who expects otherwise is going to be disappointed as Nintendo/Capcom aren't going to alienate a legion of fans who will expect nothing less than the Ryu they know and love.
I am a big fan of the EX gauge idea personally. Its inclusion would be an interesting gameplay mechanic for him, and a welcome reference to his original series. In some sense I think it would be a shame if they didn't use it because it would be a fun and unique mechanic in the game, especially if it acted similarly to the games in that it didn't give much extra knockback to his attacks, but increased opportunities to lengthen combo strings.