If bmi regional were to go
I don't think losing bmi regional would cause a loss or noticeable drop in pax numbers as they share:
Heathrow with BA and they won't get to keep that route anyway.
Manchester with BE would lead to increases in capacity on that route.
The BD flight to Norwich is already being operated by T3.
Esbjerg and Groningen could be picked up by Eastern. These are low pax, high yield destinations anyway. 10 pax on a flight.
Anyway judging by the news it looks like the BMR sale is going to move at snails pace.