I just wanted a way to replicate this image on the tabletop, tbh!
This is an addendum to the first paragraph/scentance of the normal HHW rules from TO:AU&E, page 127 -
Alternatively, a Mek may carry a Handheld Weapon of up to half of it's total cargo limit (5 percent of the unit's total weight) in a single hand. While carrying this Handheld Weapon, the unit cannot make any punching or pushing attacks with the occupied arm, use any physical weapon beyond what the Handheld Weapon mounts (if any) in the occupied arm, or use any weapons mounted in the unit’s occupied arm.