gmeyer, you and i should talk sometime during the week. i have some designs that might interest you.
reliable: consistent performance - shot to shot consistency. bolt catch should never fail to catch on last round. mags should not leak, ever. feeding from mags should never be a problem.
durable: 10k+ cycles without failure. components should not destroy one another.
accurate: mechanical operation/BB flight path.
practical: a system inside the bolt that can adjust the power output to the BB/barrel, while maintaining consistent cycle operation. the adjustment needs to be done with a tool that is part of the carrier, and not some ridiculously long and impractical allen key hybrid that scratches the barrel. (i have a working prototype of such a system)
a CO2 mag with internal regulation should be easy to do. the design would have to be different than current cast/cnced mags. two chamber system - one for the CO2 cartridge, and the second for an expansion reservoir with a regulator in between the two.
the valve lock (keeps the mag's main valve open) should be part of the lower valve striker group, not on each mag. should reduce the cost of the mag a bit. the mag it self does not need to be made of solid metal to withstand impacts from being dropped. make the mags light by using polymers for the inserts, and only use metal where high pressure gases are routed.
designs i have, crude prototypes i have made and have tested. i lack the capital and equipment to produce a viable product.
Weapons Technician / Gunsmith
Don't look at me, I don't know, lol ¯\(°_o)/¯.