I've never paid attention to haunting presences and the Haunt Shift spell. It came up in an old thread I was googling about True Seeing vs Mindblank, and I started looking into it.
I found JaronK's write up on holding holy/unholy arrows + Kiss of the Vampire + Haunt Shift, etc.
But I had another idea... keep in mind I'm coming at this primarily from a DM perspective, concerning monsters, not player characters.
Beast of Bane (Shadowdale: The Scouring of the Land), as well as Beast of Xvim (both basically the same template), can be applied to any non-good corporeal creature. Beast of Bane even has an official Level Adjustment of +2. Much like a Barghest (but without the upper HD limitation), a Beast of Bane can eat a slain humanoid as a full-round action. Every three humanoids you eat causes you to gain one hit die.
So, be a corporeal undead with 5 to 8 HD, and gain the Beast of Bane template (it is an acquired template). Have Haunt Shift cast upon yourself, tying you to a suitable object. You can then use impermanent home to become corporeal when a humanoid target comes in range, slay him, and eat him. Do it a few times, and you now have the awesome Haunt Shift abilities of 10+ HD undead, allowing you to animate an immobile haunted object (well, assuming you have Cha 17; Beast of Bane even gives you +4 Charisma).
The above is basically just another (new?) way to get around the HD restrictions.
Now, here is the potentially really interesting part. I'm not 100% sure it works, but that's part of why I'm posting this here.
Make your haunted object something that can "feed" or "eat." A dead body would be the simplest answer, and a skeleton might work too. Going beyond corpses might be a bit fuzzy, rules-wise.
Poltergeist haunt your object and move/control it like an animated object. Slay a few humanoids and use your haunt shift object/body to eat them.
From all the discussions I've read thus far (admittedly only a few), the animated body does count as you (personal range spells can affect it, etc).
Congratulations, you just increased the HD of your animated object body.
