I want players to be able to salvage a character who has died, but I want character death to be something more than a momentary inconvenience. I don't want to institute characteristic penalties for revivication like D&D's CON loss. I've elected to go for a more roleplaying-based approach to character resurrection.
The spirit stays with the body for a while (say 12d6 hours?) after which time it heads off to the afterlife with the ghostly equivalent of whatever equipment it has at that point. So, if the body has been despoiled, it's going to make life — or afterlife — a bit difficult.
Warrior-peoples would expect a good, dutiful warrior to hang around for a bit and gather a sort of spiritual wagon-train of the deserving helpless together, to guide and protect them on their way to Valhalla, or Paradise, or wherever. These spiritual migrants would be prey for all sorts of nasty things: demons and such-like, hence the need for some kind of guardian.
While the spirit is hanging about, it could be called back with the appropriate magic without too much bother (apart from the inadvertent calling of demons or hungry ghosts or what-not — see below), but once it's on its way to Paradise it would require sending someone after it. That means that someone would have to be prepared to die and hope that they get resurrected when they get back with the desired spirit.
It might also be part of a full-service assassination to send someone after the deceased to make absolutely sure that he or she won't ever be coming back.
Even during the initial grace period, getting the right person back into the body wouldn't necessarily be guaranteed. There are bound to be a bunch of spirits and things hanging about who would much prefer to get back into an earthly body than to head off to what might be a rather unpleasant judgement; the dead person might have to fight off one or more such spirits to get back into his or her own body.
The condition of the body could have a significant effect on the newly-revived ex-corpse; putrefaction sets in quite quickly, and it would be kind of disgusting to wake up in a stinky, slimy, bloated body, not to mention the issues with having large parts of one's brain turned to goo. Preservation of the corpse during the resurrection process would therefore be vital unless you want a zombie.
NOTE: Resurrection is bound to tick off the gods of the dead.
Immortal creatures, such as elves, fairies and so forth, have no afterlife and cannot be properly resurrected. If an immortal dies, its life-force dissipates and is absorbed by the Earth-Life from whence it originally came. A newly-dead immortal can be sort-of resurrected, but once the attachment between the body and life-force is broken it can never be truly mended, and in all such cases the subject will gradually just lose interest in anything and fade away, leaving an empty husk which will eventually succumb to starvation and general self-neglect. In some cases (fairies, for example), the revived corpse will literally fade away over time leaving nothing but a cobwebby substance.
The body of a newly-dead immortal can still be used as a host by hungry ghosts, if it is revivified by magical means.
The chance of a hostile spirit interloper finding and attempting to capture, destroy or replace the rightful owner increases as time passes. At the instant of death, roll 3d6 — a score of 3 indicates that something is right there waiting, and the newly-dead spirit will have to fight or flee immediately. That chance increases by +1 for every hour that passes thereafter until either the corpse is revived or the spirit leaves for the Afterlife, 12d6 hours after death.
A corpse can be protected from invasion by keeping it within appropriate wards until it can be resurrected (or until all hope has gone and everyone gives up). Of course, if a hostile spirit makes its move before the wards are in place, all they will do is trap it with the body, which could be bad. Although it is possible, with the appropriate magic, to tell if there is a spirit within the warded area, and even how many there are, it is not possible to tell which is which until the resurrection is complete. The implications of this are pretty clear, I think.
Note that even if a hostile spirit manages to take posession of the corpse, unless it has the power to do so itself it must still rely on some outside agency to revivify it.
Resurrection is not without consequences for the character in any event. The mere fact of being brought back from the dead accrues 1d6 of Unluck, to represent the disapproval of the gods of the dead for spurning their domain. This is cumulative, so if a character has been killed and revived four times, he or she will have 4d6 of Unluck. This Character Disadvantage can be bought off with XP, but removing it would also require a roleplayed in-game resolution, such as a quest or something.