Smeargle @Focus Sash
4 HP, 252 Atk, 252 Spe
Technician, Hasty nature
-Power Split
-Extremespeed
-Mach Punch
-Encore/Destiny Bond/Block
Switch in on an opponents physical sweeper while it's boosting, Encore/Block if you wish, Power Split, spam Extremespeeds. Use speed EVs and Hasty nature if you're using Encore or Block, but you can switch those over to defense and Impish if you're running Destiny Bond.
You're pretty useless against ghosts, so I would consider a different type for priority. Sucker Punch is a pretty good choice in that regard, though obviously leaves a steel problem. Maybe forego the status move altogether and make use of that Focus Sash and Power Split combo by itself to leave yourself ample coverage.