How could or should the 6.5 mm Grendel be improved?

[stanc]

The question I asked before remains valid: does it need a larger case to (a) give it more energy to compensate for shorter barrels (b) to ensure it is blind to yaw and blind to barrier © so that it matches 7.62 mm across all situations with a cartridge that is the same across all dimensions except for weight and recoil and (d) to compensate for generally lower standards of ammunition quality for military purposes?

a. That depends upon just how much energy is deemed necessary.
b. I think that is a function of bullet design, not case length.
c. If it is desired to match 7.62 performance, yes, a longer case is a must.
d. Probably so.

IMO, it will be necessary to lengthen the case by at least 4mm in order to design an M27-type link that will fit properly for interface with the feed mechanism, and allow sufficient shoulder area exposed for contact with the feed tray cartridge stop.