I wouldn't know either sadly as i am totally inexperienced in modelling.
Doesn't take away that the previous message is true though.
You could ask Army in a PM (you can send PM's i hope?) or something, i know that he knows how. :)
EDIT2 BETWEEN LINES EDIT:
Spoke Army Unit just now.
He said he could only help if you are working in Blender (since he uses that himself).
I believe it had something to do with naming a bone...?
Ah well, contact Army or just ask around.
That could make things easier as you can also animate those if needed.
If you just have the hands (hands and hooks) part of the default playermodel you can include these as such nodes and hide/unhide them when needed.
Shouldn't be too difficult script-wise.
EDIT:
I just figured that indeed you guys probably didn't know since the shown bot vehicles don't have that either and i know Filipe would like to do that since he did that with most of his vehicles. :)
Anyhow, i would be glad to help, shouldn't take too long to get you guys the code needed to hide/unhide nodes when needed.
I'll submit it here once i got it done.
If you got anyone else that can do it, also fine with me, i can't start right this moment anyway, bit busy with school work.