They would look like your basic testificate villager, but with a face bandana and some rougey armour. The mob would be very rare, but more common in forests and caves and such. They'd spawn in groups of 3-5, each armed with either a sword or a bow. The chances of the mob having a bow would be ~30%. They'd be hostile at night and passive or hostile in the day, I don't really know which would fit better. They'd drop a few gold nuggets, which they obviously have stolen from somewhere else, and have a chance to drop the weapon that they were using. Maybe there could also be a small chance they'd spawn with a wolf pet(?).
Hard and nice! Since we now have someone working specifically for the AI in the game, i think they should have a base, where they guard the result of looting. So, if the player dies, he has the dillema of shrugging it off and letting it go, or going into their base to fight against bandits who are better equipped than before to get his inventory back...
New mob idea