Wiking has done some very interesting threads on alternate German aircraft, armored vehicles and WWII battles. I should have recommended you look them up myself but it slipped my mind, plus I don't have any links to them.Looking through them, it would seem it would be quite effective indeed, especially with improved engines.
I do agree that the Fw-187 hasn't run it's course yet, it will still have the advantage of superior performance at higher altitudes than most if not all Soviet single engine fighters. I would say it would keep this advantage until about 1943 when things will start to even out with the introduction of new Soviet fighters and by 1944 the Luftwaffe should start fielding a replacement if not sooner.
Again just my opinion.