I've been wondering the same thing, there aresa few monsters I wish there were minion stats for .
comparing the very similar "Goblin Cutter" to "Goblin Blackblade" MM page 136
to minionize
remove all feats ( Blackblade has improved initiative)
remove skill training ( Blackblade has stealth and thievery)
attack the same, damage somewhere around average rounded down.
some removal of signifigant power ( they remove Sneaky power and gimp combat advantage damage to 1 point).
reduce to 1 hp
This is the only example I looked at, someone needs to look at some other monster entries to see if this is consistent