Maybe certain weapons should carry a “Close” flag, and if what you’re wielding doesn’t have it, trying to attack or fire after you’ve been grabbed prompts “your weapon is too big to use while grabbed; try a smaller weapon or unarmed attack”. Or use volume for this - volume of 3 or less can be used while grabbed, higher volumes can’t.
(Since you don’t have room to swing or aim your big weapon, you’d need to pull out your knife or pistol, or start punching to try to get free.)
This would provide some use to unarmed combat, as well as knives and other close-range weapons, as something other than a novelty or a low-volume alternative to a “real” weapon.