I like the idea posted someplace above of a "handler" unit for Lunatics, or maybe even anyone with the Crazed promotion. Possibly low defense and easily assassinated. Same would go though, for Asylums, in my opinion. That is, keep "Crazed" dudes on garrison duty someplace with an Asylum, and maybe they stay there.... y'know, in their cells!
Maybe rather than a handler unit though, it'd be a handler promotion, not something too easily granted, like through the Loyalty spell. Maybe anyone in their stack who has the Law II promotion or Mind II (hey, if you can charm your enemies, why not charm your crazy armed forces) promotion, i.e. a full blown Mage?
I did find though that shelving crazed units way out of sight of enemies, they didn't run off, I didn't experiment with this too much though. Had a scout with enraged who I stuck deep, deep in the heart of my empire and he stood there the whole game, though early on (after he got crazed in a dungeon) he was chasing after anything that moved, I had to drag him back as soon as I could...