I've been sitting back on this discussion, but have to step in here. If you're arguing that it's in the name, then the game disagrees with you. An Assault Rifle is a specific thing. Specifically it is a rifle (that is, shoots rifle rounds) that has a pistol grip on it. It is also either semi or fully automatic. THAT IS THE DEFINITION.
Therefore, there shouldn't be a Tommy gun option (as Tommy guns shoot pistol rounds)
There also shouldn't be a Nemesis Rifle option, as that does not have the requisite pistol grip.
If we want to get out of just the visual element, Assault Rifles don't shoot shotgun shells, beanbags, grenades, or fire... And yet, they do in this game.
Your argument that it needs to have a weapon is moot because the game does not define an Assault Rifle the way you want it to.