Classification of the undead and the unquiet dead

[Gordis]

What say you if we try to classify the "otherwordly" beings of Middle Earth?

Here is my first attempt:

1.The Undead, the Faded - with a physical body (hröa) present, but invisible (remaining in the World of Shadow)
1a. Ringwraiths
1b. Wraiths (victims of the Morgul blades)
1c. Faded Elves, the Lingerers.

2. The Unbodied, ghosts of the dead - naked spirit (fëa) without a body (hröa)
2a. Ghosts of dead Men (Dead of Dunharrow, Helm's ghost, etc)
2b. Ghosts of dead Elves: Houseless Elves who refused the summons of Mandos
2c. Ghosts of dead Orcs "left naked on the other side" (see Gorbag's words)
2d. Unbodied Maiar (Saruman after death, Sauron after his downfall etc.)

3. The fëar of the Dead housed in some bodies not their own, or in objects.
3a. Houseless Elves "housed" unlawfully in living bodies of Elves and Men - "possession"
3b. Houseless Elves (or other naked spirits)"housed" in dead bodies (not their own) - Barrow-wights
3c. Some spirits "housed" in stones - Silent Watchers of Minas Morgul and Cirith Ungol
3d. Some spirits "housed" in animal bodies - werewolves (and wereworms?)

4. Fëar housed in visible material bodies (hröar)
4a. Self-incarnate Valar and Maiar - Morgoth, Melian, First and Second Age Sauron, the Istari, etc.
4b. Re-embodied (by Eru) Maia -Gandalf the White
4c. Re-embodied (with the help of the Ring) Maia - Sauron
4d. Re-embodied in Mandos Elven fëar - Glorfindel, and other re-embodied Elves who stayed in Valinor.
4e. Re-embodied in Mandos (exceptional case) Mannish fëa - Beren

I have already posted it on another forum, but I would love to hear the Mooter's opinion. I will edit this post to incorporate your suggestions