I got to say looking further at Project M's Roy, I think its likely how Roy would have turned out had he made it for Brawl, both moveset wise and aesthetically.
He most likely would have came back with some of his own A-moves and flashier fire (with the blade on fire), and probably his own Final Smash (Marth's Final Smash is based off of FE3, the HP meter particularly).
Aesthetically, he draws more from FE6.
Really, they did an excellent job with it.
I actually played Project M for the first time today. Its the 2.5b version of the game.
I am really loving it. To me it seems like the best of both worlds. Melee's fighting engine with Brawl's roster.
I have to hand it to them with Wario in particular. They made him feel much more like Wario (particularly Wario Land Wario) and he is now an extremely fun character to play. I also like how they changed up Lucario, Squirtle, Ivysaur, and Charizard as well.
I love also how they brought back the Metal Cavern. I have actually been wanting to play on that stage since the 64 days. Fourside was also great to see back (one of my favorite stages from Melee).
Some points of criticism. The Castlevania stage REALLY, REALLY needs a set of Castlevania music for it (especially considering how much awesome Castlevania music there is). I am also peeved about the inclusion of the SSE Jungle which seems like a very generic boring stage. I also don't like how Hyrule Castle and Saffron City had their obstacles removed (the tornadoes, and Pokemon specifically). I didn't like how Norfair was basically turned into another "platforms only" stage as well, with no lava obstacles at all. Skyloft is also a boring addition.
Personally, I want Mario Bros., Distant Planet, and Brinstar Depths back, but that's just me.
New Pork City and Hanenbow won't be missed though.
Overall, looking forward to seeing how the remaining six Brawl veterans (Samus, Yoshi, Kirby, Meta Knight, Ice Climbers, Olimar) turn out, as well as Roy (and inevitably Mewtwo).
Project M seems to fix the flaws that Brawl had and truly make it something that surpasses Melee (as opposed to something that is merely on par).