To be honest, this whole "laser wall" thing is dang near impossible to set up unless you send Bowser far offstage [Wolf can sort of start it if Bowser is kicked off, but he has to be really fast and not go for any offstage followups]. My point was that the MU basically becomes 100-0 when Wolf's firing the gun repeatedly from center stage with Bowser stuck on the ledge.
If Bowser can stay onstage to avoid letting Wolf set up, things are still... bad... but far from unwinnable [play a good Sheik as Pichu (in Melee) if you want to see unwinnable XD]. But if Wolf gets the laser wall up with Bowser on the edge, he might as well SD to get hovering over center stage with a tinge of I-frames.
I'm unclear on why Peach Bowser is bad, since Bowser practically zero-deaths her if he lands one RR [do the dthrow, combo into koopa claw, then I think fair or usmash? That's basically dead, or only needing one more hit.] but I never played Megasaturn's Peach with Bowser so I have no idea. I also don't think Falcon is THAT bad, but it's not fun either.
The only MU I can think of that seems to be good would be vs MK, and I honestly think that's just my MK being bad vs armor, not MK losing the MU. Bowser might lose almost every MU in the game to be honest, but if you don't know how to deal with him, he'll body you and make it look easy. If I had to guess, I'd say he could survive vs Snake rather well while comboing him hard, and could do well vs DDD if he can clear Waddles [I don't know if he can]. Then I think he can handle the fire emblem boys ok, and I think vs DK is just a classic titan battle, so to speak [same vs 'Zard, at least when 'Zard's fair only flinched].