I ended up using the script even though my follower had more than enough magicka, skill and the spell. It wouldn't work, I suspect the problem is that the AI will select the spells with highest damage, and bound weapons don't do damage when cast (only when used as a weapon). My follower had destruction spells too, and would use those instead. I believe that the thalmor NPCs that use bound weapon do so because bound sword is their only offensive spell, but I would have to check if that is indeed the case. Also, it is my experience that bound bow is bugged for NPCs, and I have seen this stated in other forums. I could only make it work with bound sword (I didn't try bound battleaxe). You could try giving your follower boundswordrighthand or boundswordlefthand as their only spell to test if that works. Also, so that he won't use his fists instead, make sure that in his combat style his "unarmed" equip slot multiplier is much lower than spell and melee.