Smash should just commit once and for all and introduce the most literal blue-haired anime swordsman in existence already.

Might as well see the deed through to the end and watch the world burn.

I honestly never saw the problem with Sonic using a sword, since his primary ways of attacking were always slicing through his enemies, just with his quills instead of a weapon. Besides, Black Knight was a spin-off game, so I don't see what's wrong with spin-off games trying new things if they don't affect the main series of games in any massive way.