According to a recent interview GLA will be the main source of European destinations from Scotland, slot application dependent two airports in Germany have been applied to and waiting to hear back. Assumptions at the moment at taking over the Dusseldorf route which has been dropped by eurowings and perhaps Hamburg or Hannover could be a good prediction.
As as has been mentioned Brussels and Copenhagen may be a step too far but you never know in the aviation world, I suppose it will depend on the success of jet operations.