DD,
Keep the MAN base and routes is my advice.
Unfortunately, your advice ends up being self-contradicting, even if that was not your intention.
For Regional to have a place in the market, it needs to operate routes where there is (a) enough demand to put bums on seats and generate good yields, and (b) not so much demand that another operator can come onto the route and sell said seats at a lower cost, as they have larger aircraft.
Now I don't doubt for one minute that MAN has the advantages you mention, but I think that comes under satisfying (a) more than it does (b). ABZ on the other hand is a much smaller market in terms of population, but it can generate good yields to the right destinations.
The sale, which was reportedly worth £8 million, is said to have included the regional carrier’s fleet of 18 Embraer jets.
Thought regional was the more profitable side of the group? surely these jets are worth a few million squids each - suggests regional were liability like baby?