Ehhh, that's debatable, really. Orkz have by and large already won a long time ago in canon. The WH40k universe is basically their nirvana. When they say something along the lines that they're not losing (losing would be
not fighting, not dying or having to retreat. Dying just means getting into another fight with Gork and Mork and retreating means you get to fight more later
), they're just getting blown up so the next fight will be better, they're
right. So long as conflict is possible, they've succeeded in their operational goals. You can win a fight against an Ork, but Orkz don't lose, heh. Even if you kill them.
But yeah, they can't really just magic nova cannons out the aether, and they're limited by their imagination (which is itself limited by the size of the waaaagh they get together, really, to provide the psychic juice to actually make it happen.). But a mekboy can do stuff with a pile of scape or a broken spaceship that's literally physically impossible, and given that space hulks are basically limited only by plot (because, as noted, there's no bloody telling what's stuck in that thing. Maybe there's a warp spawned copy of the Executor itself in all that junk, who knows *throws up hands*), I wouldn't wager against them pulling a doom MacGuffin of some sort out of one of the hulk's crannies. Sure, it might blow up half the hulk in the process, but Ork equipment is, well, more effective than it has any right to be (and given how terrible some of it is in practice, that's really darn telling, heh.).
'Course, as noted, they'd probably just hurl a bunch of chunks of it stuffed full of orkz at the enemy ships instead. Prepare for boarding action, ahahahaha!
So I'd say it depends on the space hulk, y'know? Some of those things take WH40k
fleets to stop, from what I remember. Executor's a
whole lot of kickass, but it's not quite on that scale, I don't believe. Galactica's a whole lot of buggered, though. I'm not even sure if it could meaningfully contribute, outside of maybe getting rammed into the Executor after the Ork boarding parties took over.