Putting Sakurai himself in Smash in any form - be it as a Spirit, meta-boss, playable fighter, whatever - would have a catastrophic effect on Smash and overall Nintendo fandom. We'd have wars between "worshippers" and "haters", (very just) cries of narcissism, Nintendo fans learning what "consumerism" and "idol worship" mean the hard way, those aforementioned fans and detractors turning sides... It'd be worse than Byleth, worse than the Waluigi AT, worse than Federation Force, worse than Grinch Leak, possibly even worse than SwSh, it'd be HELL.