A shotty with X1.5 movement speed, stacks with lightweight
MMS has a maximum range of 25 meters and can't look through two walls or spaces you can't navigate. Completely useless on a LMG.
Having a shotgun with extra speed doesn't make any sense whatsoever. You're basically allowing someone to have a permanent care package marker glitch. Lightweight would be superfluous, much like stock on shotguns.