So I've been thinking about what kind of playstyle I would want Ryu to have and man...how on earth is he not already in Smash? There is just so much to pull from.
It's almost impossible to include everything that he has without giving him some sort of "weapon change" mechanic, which I would personally be against. I'd like him to be more traditional in his playstyle. Maybe they could include the tonfa, nunchacku, staves, etc. through some of his smash attacks and tilts. In general, they probably could get most of their influence from DoA, but given that Mega Man and Simon are heavily inspired by their original appearances, I think that it would be cool if the same thing was done for Ryu. Having his classic run and jump animations would be awesome. A Windmill Shuriken neutral special also sounds perfect, as it's just a really cool attack and would translate really well to Smash. And if there is one thing from the Sigma games that absolutely needs to be included it's the Izuna Drop. Such an awesome technique.
Gosh, there is just so much to work with. Normally, I'm pretty bad at designing movesets, but I could probably make like three unique movesets for Ryu that are all completely different. Considering how much Sakurai loves ninjas, fighting games and retro characters, I feel like he would have an absolute field day with Hayabusa.