Add to the list:
removing Protect Artifact and Quintessence.
this is also a no-go area as I can recall.
Ah, should have thought of that one, thanks!
I've added it to OP.
I don't know if Zanz has outright nixed this one, but attempts to do this very often get met with heavy resistance.
Actually, there is a card in armory right now that is a weapon which removes immortal status... Its discussion was quite, animated, but its gotten to level 3.
As far as I can tell, no one seems to support removing immaterial status from permanents though.