Adamant is probably the best thing to do. You can always baton pass a speeds boost to it or give it some more speed EVs. Plus can't Mimikyu learn ominous wind? Plus can't you always use an X speed? I dunno, just throwing some ideas in the favor of adamant lolI literally cannot decide the nature on this thing. The speed boost from Jolly is good but it also seems like it really needs that oomph from Adamant.
I am really loving stacking easy sword dances though.