Xivilai 0018BA25
"Unlike regular Xivilai, the summoned version has 0 fatigue. This means that if the Xivilai is hit by anyone using Hand to Hand combat, he will fall down. "
"Oblivion Remastered fixes this bug."
The fix from the remaster could be included in the UOP.
"*Although summoned Xivilai have the "Heat Blast" spell in their inventory, they do not have enough magicka to cast the spell unless you cast a custom Fortify Magicka spell on them. "
They should be able to cast this spell.
https://en.uesp.net/wiki/Oblivion:Daedra