No if I wanted what you say I want their to be in the first paragraph, I would want the Golden Eagle. We have a F-15C modeled around Eagles from the Late 90's and Early 2000 era. JHMCS was coming out in the Early 2000's, so I see it fitting to have it for that reason. This isn't a massive version difference and comparing my proposed upgrade to the difference between the SU-27 we have and the SU-35 is well over the top. My plan is not an ultra upgraded version just a slight modification to allow the helmet sight. As for your last paragraph, 1972 (though the BIS didn't come out in the 1960's like you suggest) vs 2000's MiG-21, come on that has nothing to do with the Eagle and is such an overreach. A few years is a lot different from a few decades.
No JHMCS
JHMCS
MiG-21Bis
Upgraded MiG-21
I can do the same thing with your SU-27/SU-35 and MiG-29/MiG-35 Argument. Those planes specifically wont be implemented for decades to classified information either, unlock a basic FC3 Eagle with JHMCS slapped on.