I think the biggest candidates for a Tekken rep are Heihachi, Yoshimitsu, and Kuma.
Heihachi represents the series as a whole the best, being in every game (I think) and having already been in a crossover (PSABR).
Yoshimitsu can be considered both a Tekken character and a Soul Calibur character, so that's a bonus. He's also been in most of the games, if not all of them.
Kuma has been in many of the games, and would probably fit in best in the Smash universe, what with him being a TV loving bear. Roger/Alex would give Kuma competition, but Kuma is more important to Tekken history, if I'm correct.
I foresee Heihachi being the most viable Tekken rep, with Kuma being an AT.