8 characters is like the extremes of wishful thinking, but a little hope never killed nobody.
Pack 2, Newcomers Galore!: King K. Rool, Wolf, Isaac, Bandanna Dee
Pack 3, Haven't I seen ya before?: Snake, Ivysaur, Squirtle, Pichu (can you tell I'm reaching a bit?)
And Young Link can stay in Melee forever. Sorry, Young Link
Alternately, Inkling can substitute for one of the Pokemon in Pack 3 to take advantage of Splatoon hype.
If Pichu came back, but super buffed, I wouldn't even be mad. Unexpected king of rage mechanic. The new Diddy/Meta Knight. Search and destroy.
Yes.