Cloud1 - I think you'll find that CMF doesn't actually require a steep approach aircraft.
LCY would mean significant training for crews and with limited number of Q400's which are steep approach modded (approx 15% of the fleet), it simply wouldn't justify the slim rewards for Flybe to head back there. It is simply against their business model and far better given to Eastern or Loganair. Selling the slots could be quite lucrative for Flybe (if they still own these?) LCY is very slot constrained at peak times so there may be some opportunity for revenue from these.