[Bruno]

If the improved version consumes the soul gem instead of the corpse, that's just an alternate, less exotic and totally legal Trigger consumable. Presuming you can use white souls, of course. If it takes a black soul, we're back to illegal.

(For bystanders: "white" as in white magic, the souls are animal souls, the minor ones often collected while hunting; "black" as in black magic, the souls are from people - men, mer, etc).