Higher shot count (bottle) is always nice.
Appears big and long, but that could be skewed by the actor being a little guy.
Externally adjustable reg (as Thach mentioned) would be nice.
At first glance it makes me think the tube is plenum, ala Vulcan V3. If so, that's a pretty big plenum. All speculation here but assuming the tube is same diameter as older Vet tubes, that looks roughly the length of a Short tube. I believe the volume on a Vet Short tube is around 183ccs.....Yep, large plenum if all that is the case.
I like that the undermount pic rail has more than just 2 or 3 slots. Might be enough there to not have to immediately add an aftermarket one like so many other guns need.
There are more changes here than I think we orginally suspected. The OG Vets don't have a removable plate on this side of the breech block. This one appears to.
Cocking handle is still giving me Edgun R5M vibes.
Overall? Looks to me like an R5M, an OG Vet, and a Cricket 2 Tac had a baby.