Negative LA-Assignment : Resurrection, but no diamond here

[Metastachydium]

n your comparison, you forget that the Psychic Warrior has an armor, while you'll have a hard time finding one for the Mound

Well, armour for unusual (as in nonhumanoid) creatures is an issue explicitly covered by the rules. Sure, it would cost some and it would make the 'mound would look like a Kugelpanzer (which is not necessarily a drawback, mind you), but I'd argue that it's doable.
Magic items, on the other hand might be a bigger issue.