Anyway, I don`t understand why US dropped it, if they had a similar design already on the F-4. Any clues? Thanks

The main problem with the american system was that they didn’t have the missiles to match so basically you had AIM-9 missiles with a Field of view of less than 40 degrees on the pylon, which is well within the effective field of a scanning radar in a close combat mode. The Soviet system only really becomes useful when you add both a wide FOV (90-120 degrees in the Archer, 110 degrees for the R-27T/ET models) and of course the added advantage of thrust vector controls on the rocket motor of the Archer allow for very hard turns off the rail to actually keep high offboresight targets in view at launch.

But for the sake of discussion, I feel new features should be incorporated to the Russian HMDS. e.g night vision, cueing of other fire control sensors, if it is not already capable of.

The problem there comes down to weight. In a helo you might pull a max of 3 gs so an extra 1-2kgs for NVGs is acceptable, but adding 1-2kgs in a fighter leads to adding 9-18 kgs for a high g turn to your head. Unless you head is supported that could really strain your neck, and for what? At night you would be using radar, IRST, and off platform sources for target finding rather more than the Mk 1 eyeball. The EO system fitted to the Mig-29K and late model Flankers includes a Thermal sight, whose picture is displayed in the HUD. Adding a few computers and projecting that image in a monocle probably wouldn’t be that hard, in fact a full binocular setup would be relatively straight forward in theory… but again I don’t think it would be pivotal in combat. Certainly in navigation modes or ground attack it might be more useful…