But you can wish a unique SC from another player. I think that is what Ironhawk did to Cleveland's Lord of Banefires in one MP game I was in. Still waiting for confirmation from the secretive Ironhawk though...
That seems to be a pretty good use of a wish assuming you can subdue (enslave/charm) the SC as you not only get an SC, but cause your enemy to lose one, plus you get all the gear.