Make stunning disable teleportation powers of non-PC monsters
It is extremely exasperating to fight the D:50 balors with a L40+ Beastfighter (and, worse I presume, on a L25+ Thief). This is mainly because stunning a monster results in the immediate [almost immediate?] random teleportation of said monster. It would be much less exasperating if—instead of a monster losing control of the ability to control teleportation and teleporting randomly—stunning a monster instead temporarily removed their ability to teleport at all. They'd still stumble at random and all that jazz, but it would eliminate the huge sigh and need to hunt them down (or close the levers and walk halfway back up the corridor to lure the balor back to the lever).
This would presumably make Andor a much more tractable fight for Thiefs/Beastfighters as well.
For consistency, this would probably mean disabling teleportitis on a PC while they are stunned, but that's up to TB.