From my point of view, and I don't know about legal limitations for this, the effects in the game need a major overhaul (smokes, explosions, bullet trails, sounds). Some mods have made great improvements in these aspects, particularly HSFX in the smokes and particles area includes very nice modifications.
And maybe have the russian planes rechecked so that they are adjusted like germans, americans, british, etc.
As usual, I know it might be a lot to ask, but asking is free (for now
).