Jigglypuff, Pichu(without self-inflicting damage), Marth and Game & Watch should stay.
Ice Climbers, Ness, All clones (not luigi) should go. This means Roy, Dr.Mario, Ganondorf and Falco. Falco can stay if he has a different moveset.
All stages can stay as they are, or be similar, as long as there is NO ICICLE MOUNTAIN!