Where's the problem with 'Lychantropos Amulet', unless it's a mage who picks it up?
I don't think there's a way to keep him from berserking, and berserking commanders will not use spells
If it is a melee commander and you only need him , simply give him some protective items as well and some tough bodyguards who move at least as fast as him (check AP) ... and set him up at the rearmost edge of the battlefield.