I think the Micro-SMG gets discarded unreasonably.
While the stats (read: files, not in-game stats. Those are bogus.) may say it underpreforms compared to the Mini and the MP; It's like the Scarbine, who DOESN'T have an area of expertise which is the beauty of it. Its the "Good at everything, master of none" approach. The Bullpup fires faster, the Carbine is more accurate at long-range. The ARmk2 hits harder per shot.
The 30 round extended clip and the option for plentiful of mods while being medium sized (not that size matters or anything, but y'know. Concealability?)
The Mini has speed, and the MP has low recoil. The Micro?
While it fires reasonably fast, it doesn't spread as bad as the Mini does. The MP doesn't have the ammo capacity of either, and the drum mag has an increased reloading time for it making the whole point of the MP having a fast reload while accurate and powerful per shot at a lower fire rate sorta oddly balanced.
I ignore the AP Pistol because it uses pistol ammo.
The Micro deserves a MK2. It doesn't do what either of them do "as well" but it strikes a counter-balance point of being adequate at both.
I just wishes it had the original IMI Uzi stock.