The whole point of this is to use M80A1 - read between the lines and do a google, in the last year or two you can find Chinese ceramic plates on Alibaba. They used to only offer "plastic plates" that cannot stop M855, but lately ceramic plates advertised as "level 4) are widely available from China commerically.
The M80A1 must be able to defeat the so called special threat plates that is generally advertised as Level 3 +. This essentially outdates all the level 3 plates, level 3 compressed poly and hybrid poly/ceramic out there to stop M855. If they are looking to defeat ESAPI, this means it will be need to defeat roughly a level 4 plate.
So far nothing has published the exact armour penetrating ( not steel, put ceramic ) capability of M80A1. If it needs to defeat ESAPI, the M80A1 out of a 16" barrel must outperform a typical 7.62X54R AP, roughly a 30-06 AP. This thing must have a pretty high velocity and a hard AP core.
Now, a 12 pound before optics and 210 rounds of 7.62 will not be what I called a "light weight system" at all, unless there is a polymer cased ammo in the pipeline. Definitely won't be a weapon for fast manoeuvring. The entire infantry section will now be dragged down by more "heavy weapons". This maybe army thinking but I don't think USMC will buy into this.
The fact that if they identify 5.56 is not sufficient in AP, this means the new SAW coming in 2020 will not be 5.56. Hauling a traditional cased 7.62 SAW is too heavy and clumsy, so it will need to be a plastic telescope cased in 6.5 in "light" AP format. The telling story is that if the DOD is really worrying about defeating ceramic plates and going this direction, we will be seeing the demise of brass cased ammo in the near future as a much more definite event. We may also be seeing a come back of 20 and 25mm light weight programmable fragmentation weapons.
As insidious as it sounds, we may actually have to subscribe to "severe wounding" with fragmentation weapons if armour becomes too wide spread.