[Burnsaber]

I'm not sure if the special ability of the Lammashta's "unloyalty" is in the unit itself or the spell. If it is in the unit, you could just try copystatting the Lammastha unit and see how it goes (although there is that undead "tag" you can't get rid of).

Like Foodstamp said, you could also make a commander that gives the "Confusion/Rage" debuff on himself at the start of combat, which would give the commander a 50% of attacking own troops. The downside is that the unit would move like drunkard.