Has anyone used a Telekinesis staff as a Magicka reserve for an Atronach? Charge it up when you can and absorb the spell when needed.
No, but I do use a custom TK spell for that. I'm not sure if the staff would work, since you are not actually casting the spell. I might test it since all my characters use that sign.
I
always take the Paralysis staff, and will definitely be doing so on my new Alchemist character who relies on Poisons and Staves for combat (the only magic he directly uses is Weakness to Poison and Soul Trap).
My mage-types don't need the damage staffs, and all my characters run up Speechcraft and Personality so the Charm staff is essentially useless.
The main reason I take the Paralysis staff every time is the ridiculous cost of the effect; I greatly reduced it in my game in order to test a custom spell with it, and even then it was still prohibitively expensive to use on a regular basis despite having a custom refill spell handy. As for custom enchanting with it? Fuggeddaboutit, unless you want a weapon that never has more than about 5 shots, and that only with a Grand Soul powering the enchantment.