Ah, right, forgot about Zelda and Wario... Anyways, Sonic's dsmash is different this time around.
Some of these are small changes like
and
while others have almost had their playstyles totally reworked.
are arguably the best examples of this, with new attacks or changes that have made them either play differently than previous installments or give them options they didn't have before. With a SoPo solution for the Ice Climbers, the only thing that would absolutely have to change is their belay recovery because everything else can be buffed or tweaked to make them competent with a solo climber. For example some people have suggested a condor summon similar to Olimar's pink pikmin recovery. For a Nana summon solution, the only attacks it seems necessary for is the belay, squall, and possibly the final smash so it wouldn't be a continuous strain on the game. All in all, it's doable but it's a matter of if they want to go that route.