I've never really heard of Xenoblade, but Shulk doesn't speak to me personally as a character I would look at and think he's a memorable character design, but maybe he has other motions in his home-game which would make him stand out more alongside all the Pits, Links, Cloud Strifes and Soras.
In Xenoblade characters sort of work as a team. For example Shulk has a move that induces a status to an enemy, and depending on what that status is the AI will do a attack to take advantage of that. For example there's "break" moves what when inflicted on an enemy will cause them to trip if attacked by "topple" moves, which Shulk doesn't have, but the AI does.
I'd be interesting to see if that could somehow be worked into his moveset, that depending on the order of the moves, the enemy is affected differently.
He can also
See the future, and its a gameplay mechanic too, but having trouble thinking how would that work in Smash