Very nice!

I think you could possibly improve mobility if instead of attached rectangular handles you made detached spherical handles and placed them squarely in front of the wrist, like in my messer_6. The pivoting joints would go onto these handles instead of the shaft. I would try to make it so grabby hands just barely touch the shaft and aren't pushing it away.

Also I think you might get more mobility if you re-aligned the weapon so that it is perpendicular to the forearms, i.e in the way of the wrist axis.

Great job though