If something needs a chance is the 120. Both R-27 and Aim-7 and Aim-9 are working more accurate. If they end up nerfing the SD-10, they must also nerf the Aim 54, right?
This is not a question of balance, it's a question of realism. The 120 isn't realistic so the 120 needs to change. Not all of the other things. It's simpler to change 1 missile than the whole fleet.
If you still feel uneasy about your plane performing worse, just keep it in the hangar. Not everybody plays competitiv multiplayer games, some even don't shoot. They just need accurate assets for the own module.