For this i think you need to remove all "such" teams like Luxembourg, Letonia, Slovakia teams, because they really slow the game and it`s frustrating to wait about 1-2 minutes to get into a new week. Just put all first 15 european leagues and best teams from others.
The performance problems, seem to only be on windows systems. We should see if we can improve that. Remoiving countries will diminish gameplay IMO