I've mentioned a few times in the past that this is the roster I would've given Smash 64.
Samus is moved to unlockables (I've heard she was somewhat of a mythologised character at the time, so an unlockable role seems fitting), Wario is a starter, (Don't really need to justify including Wario on its own, the colour version of Land 2 had just launched and 3 was around the corner so Wario's popularity was at a high. Having one of the Mario spin offs be unlockable would be a little weird when the rest are starters and none of the other unlockables are second reps or spin-offs) Duck Hunt (renamed "Scent Hound") and Muddy Mole are new unlockables, (Duck Hunt came out 15 years before Smash 64 so nostalgia would be blooming for the character, Muddy is somewhat of a shill pick having come out 2 years earlier in the US and 3 in Japan) and Falcon; Jiggs; and Luigi are gone (the second reps were removed to make space - I'm not in the "remove Puff" crowd - while Captain Falcon's inclusion in Smash has always been a little strange to me)

Samus is moved to unlockables (I've heard she was somewhat of a mythologised character at the time, so an unlockable role seems fitting), Wario is a starter, (Don't really need to justify including Wario on its own, the colour version of Land 2 had just launched and 3 was around the corner so Wario's popularity was at a high. Having one of the Mario spin offs be unlockable would be a little weird when the rest are starters and none of the other unlockables are second reps or spin-offs) Duck Hunt (renamed "Scent Hound") and Muddy Mole are new unlockables, (Duck Hunt came out 15 years before Smash 64 so nostalgia would be blooming for the character, Muddy is somewhat of a shill pick having come out 2 years earlier in the US and 3 in Japan) and Falcon; Jiggs; and Luigi are gone (the second reps were removed to make space - I'm not in the "remove Puff" crowd - while Captain Falcon's inclusion in Smash has always been a little strange to me)