Yea, pretty much I can't see it being taken as it should be.
Thinking over it, it'd be something along the lines of the Tiefling issue, yes. By most lores, if I recall correctly they're ostracized outcasts with heavy hearts and stuff because everybody can tell that they're literally hellish, but everybody just plays them like they're normal people with horns. Everybody'd be nonchalant about a bodily feature that could get us burned at the stake, which is really a shame.
To me, stealing it feels too much like... a mage messing about with magic that isn't of their own color. ><
I don't want to cast spells or handle magic that isn't Ulgu. That's bad juju that usually leads to dhar or corruption or at least fuckups or problems, right?
These sound like the words of a coward.
More seriously, while your general concerns are very understandable (and perhaps that's not the best phrase; it implies 'oh I know why you think that, but it's not actually correct', when I really mean more that you're raising very reasonable points here), I think the general mindset of Stealing it is that we've already skipped past most of those hurdles. That is, we already have a handle on what we'll do with the energy, more or less; when we came into the room it was cloying and electric, but now it's infused us because we just served as an inadvertent avatar for an Orkish religious confrontation.
Something about the energies in the room have changed... no, you realize. The energies are the same. You have changed, and the energies that once burned unpleasantly against your senses flood into you, your muscles bulging as power is stolen away from the Idol Of Only Gork.
With bare hands you reach out and you tear the Idol asunder, unleashing the accumulated Waaagh! into the world. And in an instant the terrible purpose that filled you vanishes, and you find yourself free to act as you will once more, and at the center of an imminent maelstrom of unleashed energies.
The option to steal it is really just to do what we've been doing with the rest of it we just unleashed. I.e we were already stealing power away from the Idol by doing exactly what Mork would have done and inadvertently serving as his champion, and it only made us stronger, so the vote is whether we go full-bore with the Mork's Champion mantling or go 'I'm Mathilde, but thanks for all this power anyways'.
And I don't want to see the results of someone with Magic 7 channeling high-end battle magic or owrse equivalent energies. I would rather get help where we can find it.
Then, I would actually suggest you go for the belt. Stealing the energies is not asking for Ranald's help to save us, it's going 'Hey Ranald, you know how you like stealing things? You're going to love watching me do this!'. It is not one of the less-blowy-uppy options.