There's two parts here, flying for BMI and flying for STAR partners. BMI flying is ending soon, regional flying to CPH, ZRH and BRU is not. If they are to continue serving these destinations, they cannot afford to have SAS, Swiss and Brussels Airlines come in on their own metal. If they get into a flybe franchise, their former partners in STAR become the enemy surely?
Nor can they keep one aircraft at GLA alone to fly GLA-CPH, now that GLA-LBA has gone, there's only one rotation per day for the aircraft.