That's exactly why it needs to happen. Smash needs Western representation or it's going to be stuck as one of those eccentric Japanese games. It'll sell like crazy but it will be a poor representation of Nintendo's global appeal.I don't get why people think Doomguy or MK characters are viable. No playable character has ever come from a western dev, and that likely won't change. Shovel Knight and Shantae are western developed games that closely mimic the Japanese style, so those are exceptions, and even then they are assist trophies and spirits.
Banjo is the one exception to the rule that might happen simply because of Rare's relationship with Nintendo up until the GameCube era.
That said I don't think Doomguy will happen, but a Mortal Kombat character would be great. Blood and gore aside, Smash and MK have a lot in common. Like massive singleplayer content.