The targeting is good so the issue must be inside the interaction.
Does adding IT_REQUIRES:FIT_FOR_RESURRECTION on the target part helps? Otherwise perhaps attaching a stand part on the seed (and keeping the seed as an upperbody)?
Otherwise, if you replace RESURRECT by ANIMATE, add FIT_FOR_ANIMATION in the interaction and give GRASP to the seed, does it work?
Thanks for the pointer to animation. That got me out of the ditch and making at least some progress. As it stands, I can animate the germ if it is a GRASP part (and since it's basically a 6kg ball of skin that's a bit disturbing to think about). Mysteriously, the animated germs are "friendly" creatures regardless of whether the dwarf had an OPPOSED_TO_LIFE tag or not. I think I can fix that by just sticking the OPPOSED_TO_LIFE syndrome into the interaction. At the moment, the animation works on any GENERAL_POISON creature, I need to troubleshoot if I should be targeting a DWARF or targeting an AWAKENED_STONE. Leaving it at is would cause havoc should one of these things appear near an old battlesite.
Resurrecting, thus far, has been fruitless. But I *can* transform the animated germ into a full-bodied member of any Awakened Stone caste. I can't tell from the UI if the transformed creature is considered an animated corpse or not, but it's "race id" in DFHack is the same as any other Awakened Stone and the "civ" is -1.
Irritating glitch 1: The germ retains its original tile (that of a severed bodypart, ² in vanilla) and its original name (such as "Urist McMiner's germ") despite having the bodyparts and coloration of a full Awakened Stone of the appropriate caste in its in-game text description. I know from intermediate troubleshooting steps that if the germ animates into a Dwarf, it does use some graphics set icon. So, I can work around the glitch by making a (1-tile) graphics set and renaming the bodypart to "awakened stone".
Irritating glitch 2: Despite the progenitor being IMMOBILE, the germ lands 0-6 tiles away. Might have to dial down the progenitor's strength a lot and/or dial up the relative size of the germ.
Irritating glitch 3: Is there a way to suppress the transformation messages? Right now I have the progenitor's caste name as "mining incident" as a kludgy fix.
So I think I can get to a workable version of the creature, though help with any of the irritating glitches would be awesome. The next major hurdle is the Tribute workshops. I know it will have an interaction that creates a boiling stone that creates a syndrome, but I haven't seen where I can add a CREATURE_CLASS tag with a syndrome. Or am I stuck with SYN_CLASSes? The plan is to use that tag to control whether the Awakened Stone is friendly or opposed-to-life.
Edit: Clarity with irritating glitch 1.