Honest suggestion, maybe Arthur's up special shouldn't be a recovery move at all? The Crossbow from SGnG seems like a good candidate, and Arthur's never been known for his jumping prowess (when you die in GnG it's usually because you messed up a jump). I also think he should have mostly ranged moves even for normals, like Mega Man in Sm4sh. Having a character who can bring down absolute death from a distance but has terrible recovery if the opponent gets in would be a fun dynamic, I think.