The goddess of death does not like undead that are not free-willed.

The lawful good gods are not fond of undead animated by negative energy.

The elves are not divulging secrets of their undead animated by positive energy.

But you're a gnome faced with the task of preserving somebody beyond death.

What to do? Well, you've got a recently deceased corpse, a Magic Jar, some Unguent of Timelessness, the services of a taxidermist, and a lot of clockwork.

Enter the Clockwork Undead. Not a true undead as one considers the traditional "raising" process - but more a way of making a vessel for a soul out of its own former body. Sharing attributes of free-willed undead and constructs, they also have, due to their clockwork nature, a vulnerability to chaos-infused insults. They may suffer a bit from a dip in the uncanny valley, but they never end up looking like apple people or smelling more off than maybe a whiff of naptha.

They do get a little doddering after a while, maybe a thousand years or so, but that's more because not many people usually stick around that long in a Magic Jar. The rest can be touched up with glue, a few screws and a touch of paint.