While playing , I thought up of a pretty interesting idea. I had posted it to the discord and Allen Stroud had directed me to the forum.
I just finished my run on Fort Freiheit. I found that I could pickup the crab guns ( as said in the game guide) but I could use them (unlike what the guide said) they’d break after one use. They did damage my enemy, at least the first two did. Neither of them had the negative bug glitches I’ve seen posted here before, either. The third one I grabbed did injure my heavy soldier and send him into a buggy teleport one-square jittery state. I honestly thought it would be cool to keep them usable but break like that. Realistically, a creature that shot a projectile using one of it’s arms really only needs a muscle pulled to fire, if it’s similar to the way real-life crabs work when you wanna move their pincers, you just grab a bit of their muscle and it’ll react similarly. (For the record, I’m talking about when you’re eating crab, my dad used to do it all the time when we’d go to Chinese restaurants )
Hahahaha, I know exactly what you mean about playing a puppeteer with cooked crab. 
In terms of the game though I think the crab weapons are at a fair place in terms of their stats. I wasn’t able to use them but their damage was about half of what an assault rifle could do. It did have the bonus of a chance to shred armour but if the grenades and heavy gun are anything to go by that’s not worth much, hahaha. I think it would make sense for them to be mission only items with limited ammo that can’t be reloaded. So, you can only get them if you pick them up from an enemy corpse on the mission and then they only have 2 shots. The exception being the crab claw, which has enough risks in using it (getting up close to an enemy) that it can afford to be used infinitely. Though I’d hope the soldiers get their own melee weapons sometime soon and wouldn’t need to rely on random crab parts, haha.