Honestly, I hope Masked Man does make it into Smash Bros. because of how Smash Bros. essentially is the catalyst for the Earthbound series' popularity.
1990's, Earthbound was considered a commercial failure. "What's an Earthbound?" People hardly know what it is.
Come SSB64, where Ness is a playable character. "Wha--Who is this kid?!" Some people take the time to try him out and actually like him. Some of those people take the time to try Earthbound and love it.
Come Melee, where Ness becomes a starting character, gets two of his own stages, and has additional trophies detailing characters from Earthbound. "Hm. This stuff is pretty interesting!" More people take the time to try Earthbound and love it.
Come Brawl, where Lucas is a starting character, gets his own stage, and has both a boss and a level-hazard taken from his game. "Oh wow, there's more than one Earthbound game?" People take the time to try Mother 3, translated entirely by the fans and them alone, and love it.
The link between the two series becomes inseparable. Smash Bros. hooks those interested, Earthbound and Mother 3 cement players into feeling like a part of the fandom. It's a cycle that works excellently. If we get the Masked Man in the next Smash Bros., we only repeat that cycle. People take interest in the Masked Man for being cool and mysterious. People try Mother 3 in a rom and end up falling in love with it, especially after seeing the Masked Man in action. Word spreads about Mother 3, fan interest gets started, ports are made (like Earthbound on the Wii U VC), vocal attention happens, remakes are considered... It entirely does more good than it does bad. So come SSB4 and people see the Masked Man and think "Wait, he's not using PSI in most of his attacks! Maybe I don't know everything about the series!", give Mother 3 a try, and see for themselves why the Earthbound fanbase is one of the most devoted fanbases out there.
Aside from his major role in Mother 3 and his capacity to fight to the same caliber as everyone else in the Smash Bros. cast, his inclusion would bring attention to a series that certainly could use it. And that's why I think he should be added.
Especially over Ninten.