Brawl Meta Knight is going to win. When people say that Melee Fox is going to win, I laugh. Why? Because Brawl MK has longer range than Melee Marth and on top of that, transcendant hitboxes that are also disjointed. Meta Knight could air camp the hell out of Fox with Dair and Mach Tornado alone would be very annoying for Melee Fox to deal with. Remember, everything except for Dash Attack and Glide Attack. Mew2King said that Brawl Meta Knight is the only Brawl character that feels like a Melee character, and proceeded to call MK "crazy good", and he never said that for Fox in Melee.
Pikachu 64 is very underrated. He could easily beat Bayonetta and Melee Fox. We already know that Pikachu either goes even or beats Bayonetta in Smash 4, and Smash 64 Pikachu is basically a hyperbuffed Smash 4 Pikachu. As for Fox, in Smash 64, Pikachu can chainthrow Smash 64 Fox to over 50%, and with Melee physics affecting Melee Fox the way they do, Smash 64 Pikachu could probably chainthrow Fox to even higher percentages. Pikachu also can edgeguard and ledge camp better than any other Smash character other than Brawl Meta Knight. Smash 64 Pikachu, by this manner, could ledge camp Fox.
Fox himself is the wild card. Melee Fox is incredibly good, but he does have a few problems. Both Bayonetta and Pikachu could very easily kill him, but Fox himself could also kill them at very early percents. Of these, he probably does best against Meta Knight, the one character who isn't combo oriented, but would go even with MK. Bayonetta would lose slightly to Melee Fox, as he nullifies her camping abilities and autocancel lasers force her to play offensive, but the matchup would be manageable due to Witch Time and her Bayo combos. Pre-Patch Bayonetta would win this matchup though. Overall, Fox would on average go even with these characters.
Lastly is Bayonetta. She would do best against Meta Knight, but they would still go even, due to MK's transcendant priority. SHe would lose to both Melee Fox and Pikachu.