Alright, here's the idea (Inspired by the fact that a double Magic Jar means that the 2nd body is your true body. Also, Haunt Shifting.)
The Crazy Method
1. Haunt Shift at as early a level as possible. I suggest being a necropolitan and paying for the spell. Make sure to pick an area; it just makes this nice.
2. Mind Jar twice as soon as you can. I suggest picking a nice first body, and a lame second body.
3. Destroy first gem, don't care because you dispelled a spell that you weren't under the effects of. Destroy the second gem. You are now permanently in the second body.
4. Because spells only check for applicability when they are cast, and Haunt Shift is Instantaneous, you still count as a Haunting Presence. Why is this good? Because Haunting Presences can only be removed in three ways:
a. The destruction of the area; you're probably a spellcaster, and you can see and hear as a normal human up to 60ft away from your area, so you don't even have to waste time on guards.
b. You can be destroyed normally while using the Impermanent Home ability; simple, don't use it.
c. You can be exorcised, which basically forces you to do b.; honestly, they just summoned a rather pissed wizard; no sane group would risk this. Besides, you have 10 rounds to wreck their shit.
And nothing else can hurt you. Nothing.
Now, a word on Impermanent Home; it doesn't really specify that you go back into the location/object at the end, it just means you regain Haunting Presence status, meaning that you can basically use this to teleport places. For no cost. Your level times a week. All it does is drop your invulnerability until you take a move action to regain it.
So, what do we have here? A nigh-indestructable wizard (probably of the Red sort) that can animate objects within his sanctum, and teleport anywhere in his Sanctum as a non-action (I'm assuming a free action.)
Also, another funny way to do this; Haunt Shift into an area of sand. Cast Awaken Sand on it. Enjoy.
So, any comments on this trick?