Hard Choice: This I like.
Holy Relic: Okay, stop. Please re-think what you've just suggested. Liches are Undead, and an item they use is highly magical. While I do understand that you'd want lich-hunters to not destroy it, you're leaving an Undead surrounded by Undead-turning Clerics. That's the worst place ever to store it! Even if it's not just them, their spells and the potential for a deity to send a vision of the desecration of their relics... I just think that it's asking for trouble in a temple filled with people who can *contact other plane* or detect undead.
Crown Jewels: This I like, because it doesn't necessarily imply a cleric. In theory there is one handy, but likely it'll be fighters and suchnot, maybe a wizard. And, of course, cunning rogues looking to steal the crown jewels. They go missing and a pile of interested parties go looking for them: the theives guild, the royal guard, and a cult of mages working for the undead monster who founded them...
The Sun: Hard to enchant pre-undeath. I don't know how potent fly spells are, but cold and lack of air are killer. Granted, interesting concept for a sci-fi d20 scenario: a lich lost in space attaches to the hull, hilarity ensues...
Imprisonment: does this work on objects? Would the Lich be trapped in the spell if they were slain, and so wouldn't this also be awful?
More important: What are the destructive forces PCs have at their command?
Disjunction
Dispel Magic
Greater Dispel
Offensive Spells (that damage objects)
Weapons
Adamantine Weapons (ignore hardness)
Volcanoes (mt. Doom et al)
Sphere of Annihilation
Disintegrate spell
Toss into the Positive Energy Plane
Terrasque's belly
Bag of Holding + Portable Hole
Wish it destroyed
will of the gods
polymorph into something destroyable
Antimagic field to get rid of its buffs, them smash it.
Confused the GM into thinking you destroyed it at the end of last marathon session...