Personally, I guess the last 3 picks are really bad (steve doesn't fit the smash aesthetics, DOOM has literally zitch for game charm and who would even pay for hasabusa?)
At this point, there's no such thing as Smash aesthetics, Steve fits as much as Bayonetta, Pac-Man or Mr. Game & Watch. The art staff in Smash is amazing at making everything look cohesive.
I think Doom Slayer, Steve and Hayabusa make a lot of sense, much more than Joker in fact. They're all from games that are very important to video game history (following that criteria, I honestly I can't think of a better western character than Doom Slayer), they're all from games that had some importance on Nintendo hardware (Steve not so much but anyway) and they're all from companies that Nintendo has good relations with.
I know the rumor doesn't hold much water but, they would be good picks IMO.
I would really like to see Ryu Hayabusa being re-imagined, based on his NES version like was done with Mega Man and Simon though, but I don't think Koei Tecmo would allow that.