I really don't think this is necessary. As much as I would love to be able to equip mercs with entire sets of gear, they are already buff. An act 3 cold merc can farm Normal and Nightmare cows on his own without much, if any gear. An act 2 Holy Freeze merc(nightmare defense) is really strong in HC. Throw a Reaper's Toll on that guy and the mobs are almost completely frozen. If you really want to have a strong tank and spank experience, just run a Golomancer