Simplicity (if cross compatible) is often the way.

Guess you will see what track to go with.

I'll do a couple of experiments and see if my idea works

The big problem will be deactivating the flash-to-ash effect when the spell expires, but I have an idea for that. If I can do that, it's just a question of reapplying the reanimation effect with longer duration and lessened health and forcing the reference into the quest alias that enables the dialogue.

Failing that cloning the spells is easy, but I'm loathe to add them all in a lump, since it gives lvl 1 chars access to Dead Thrall. So I'd probably end up catching gain spell events and adding sexy equivalents, which brings its own complications....