Pretenders can't be turned into mummies. They can be called back from the dead of course, so have fun VotDing that 0-path Wrym, it'll just cost it some gear.
How about immortals? Does the assassination bug leave them dead if they get VotD'd?
You don't have to retire from active duty with 'Ritual of Returning' in effect. It only triggers when you take damage. I'm kind of expecting that 'death by turn 50' won't trigger the ritual though, and instead would leave you just dead. I don't expect that you'd actually take combat damage from the VotD combat.
Edit: About the 'Honeypot' plan ... I don't think it makes a whole lot of sense with the current VotD implementation, since surviving a VotD by killing everything doubles the amount of undead in the next VotD battle.