It needs a safety button with an oversized flat screw on the small end so that the safety stays in.
It needs only 1 or 2 sizes of common hex bolts, the first model is a pain to tech.
The regulator needs a bevel on the cylinder edge to keep the orings from getting cut.
I would love to see a snap lock & pivot that replicates an m79 action
A ladder sight would be nice
A 2 inch PVC adaptor for the barrel would be good