We do have heavy weapons as commandos, but clone commandos rely on being able to move quickly and hide. carrying around something that requires any kind of set up just counteracts that goal. this is not to say we don't find and use automated turrets against their owners or such as it is. But typically we carry around rifles or heavy rifles at most. Commonly the DC-17 because it can do a lot. We could just invent another addition for the DC-17? 

it has the carbine, sniper, anti-armour, breaching. We could add, I don't know, something that turns it into an assault rifle of some kind?