Also, just like I thought, the second Fighter pass comes with stages and music, which is another heavy hit against Geno’s chances. Be realistic here, how actually likely is a Super Mario RPG stage? Not likely at all. Same goes for Waluigi.
Starts with Bowyer's Arena deep in the Forest Maze (when you first get to use/officially meet Geno). The stage itself isn't too interesting, outside of being on a giant wooden stump with the background being trees, maybe with some platforms elsewhere. Arena will also shift randomly to other areas, making the background and references awesome. It can go into Mushroom Kingdom, Bowyer's Arena (obviously), Nimbus Land, Barrel Volcano, etc. Plenty of places it can go.
What's actually interesting, is the mechanics/hazards. Bowyer's area has his three buttons and each one turns off a function for all players, but instead of A/X/Y, it would be B (Disables Specials/B-Moves), S (disables Smash Attacks), and L/R (disables Shielding). You'd see him shoot arrows in the background and they would hit one of the buttons just like his boss battle.
When the area morphs, it could have some kind of mechanic or hazard/enemy tied to that area. Mushroom Kingdom for example could randomly rain (making it harder to see) or have Mack and his Shy Guys bouncing all over (they could injure you and you could attack them, kinda like Magicant's Flying Men). Nimbus Land, Dodo tries to kidnap people (and damage them), or just peck at them from off-screen. You can also add the fan enemies that show up here and Birdo could spit eggs.
These are just a few examples of how they could make a stage as a love letter to SMRPG and all its references, and I'm just one idiot who
doesn't develop games for a living. The fact that fighters come with a stage doesn't remotely hurt his chances.
Waluigi on the other hand, that's a bit harder, though I could see them using a (or multiple, that morph like my SMRPG idea) Waluigi-themed level(s) from other games, such as Waluigi Island (Mario Party 3), or Waluigi Pinball (Mario Kart DS).