Garrison duty is an interesting idea. But since you need 100 men to prevent a bandit attack, I would need 100 1-man peasant units, in a minimum of 7 stacks.

The peasant might be useful as a way to waste enemy arrows. I could run him around near the enemy archers... In loose formation, of course. In fact, the unit is guaranteed not to rout due to being shot at - it will stand firm under the hail of arrows until every man is killed.

Also, it's a valour 2 unit. If the AI ever tries to flank me with a 1-man peasant unit of valour 1 or 0, I would have the perfect counter.

In spite of all this, I did not hire him. I'm pretty sure I already disbanded him once - he's a Muslim peasant, and I'm the only Muslim faction around for some reason, so he's likely to be one of mine. He was probably a unit leader and I couldn't merge him into some other unit due to a virtue or vice.