Corpses seem to be always treated as objects, although to my knowledge there isn't a hard rule somewhere saying 'corpses are objects.' The obvious answer is 'no, corpses are objects,' but I was wondering if RAW I can use a spell like Planeshift, a spell which doesn't have an effect on the actual mind, life, or soul of a creature, on a corpse.
(Trying to store corpses in my Demiplane for animation later)
Corpses aren't well defined by the rules.
Since Raise Dead has "dead creature touched" as a target, we can assume that they are both objects and creatures.
Thus, I would allow it.
Plane Shift doesn't have a weight limitation - it's only requirement is the amount of creatures you can shift. Assuming you're going with the ruling that corpses are purely objects you could load up a pack horse with a corpse, plane shift the horse, and the corpse would "come along for the ride". As long as the corpse is attended it would be included in the plane shift effect, just like any other piece of gear.
Assuming you go with the "Corpses are Creatures" interpretation, you could load up a bunch of dead guys with all the gear they could carry in life, and then teleport away with them.
It... really is a strange rule problem, but it is tradition?
Assuming they go with the "Corpses are Object", might I suggest you plane shift them before they die? Small chance they recover and eventually heal on their own and survive by eating the rotting flesh of your other acquisitions, but that's life sometimes.
Lol'd at 'but that's life sometimes.'