The combat shotgun was equally useless in kf1 and remained so to this day, so I'm doubtful TW will do anything since they seem content leaving guns in useless states. (Sorry for bitterness, I really wanted the combat shotgun to be useful).
If it where up to me to make it useful I would say make the combat shotgun hold 8 rounds and give it a speed loader like in this video.
https://youtu.be/M3Hs4do69ms
Neat video, it looks a quite cumbersome but also very cool.
About the M4, what if it came loaded with another ammo type like flechettes, APDS, that fin stabliced explosive round (don't know the name sorry) or some crazy bile-filled slug? That would make it pretty different from the AA12 and add some new options for Support class depending on exactly what the new M4 round would do.