May I add a suggestion for the design?
It would be great if your upper shells had a quick and sturdy barrel change feature, at least better than the Dolos system.
I was going to start a thread about QD barrel systems. They make a lot more sense on our guns than an AR. From my quick search the most promising ones were the LEO Takedown and Dolos 2.0. Some considerations would be if you want to have the handguard and barrel married or if you want to be able to use one handguard for several barrels. How expensive or available is the barrel side of the mechanism because several will be needed for our purposes. Is it able to be easily removed while hot. I think a system not unlike the Fightlite MCR is probably preferable. Something that would work with a standard barrel, with no added piece, would be awesome.