Move Creation Workshop

[China]

If you want extra arms, just get an 'extra arms' move instead.

Uh... yeah... buy a move for extra arms... suuuure...

...

@Dane - Some variation of these are what I believe 13 is trying to get as a move: http://warhammer40k.wikia.com/wiki/Mechadendrite
And he shouldn't need to pay extra to use each additional weapon with them, it's literally just an extra arm or two.
The only drawback it needs is that it costs him just as much energy to lift things with as a normal arm would.

@13 - Are you just spelling 'Mechadendrites' wrong, or are these 'Mechendrites' actually a separate thing that I can't find on Google for some reason?

I'm not very knowledgeable about W40k, but based on the artwork I've seen, Tech Priests (who are way cooler than Skitarii btw) seem to only ever have one Mechadendrite each... that's not to say that you can't have two or even more if you want, but I imagine it'd be pretty awkward moving around with a whole bunch of massive metal limbs attached to your back...

EDIT: Ignore the striked out text... I didn't actually read the page I linked until after posting.
Two Mechadendrites (or two 'sets' of Mechadendrites, depending on how you want to phrase it) seems like it'd totally be in line with 40k cannon.
So... yeah. You make it that lifting stuff costs the same amount of energy as lifting it would with a biological arm and you're probably good to go... well, and mention how large the Mechadendrites he's using are... including a picture might be a good idea if you can find one you like.