Actually if the player did try this and for some idiot reason the DM allowed it... The twice your HP in temp HP rule kicks, they make Fortitude checks every round and the eventually fails and promptly said player explodes... which means they are at half HP if the make their save and hit anyone near enough with a burst of (in this case) negative energy. Not to mention this requires the 9th level spell (or equivalent) Shape Change, to actually get the abilities and not just the shape.. into a legless spirit or the ability just fails. Then their is the whole literally contagious, gibbering insanity thing allips (a spirit of one who went completely insane and offed himself) do... So your clever plan ends up with a party full of people in a nightmare filled insanity coma or very annoyed at least epic level PCs... So basically this player would have talked himself to death and won a Darwin Award... and probably ended up an allip for real!
So really death by cunning plan.
So really death by cunning plan.