Realistically, in the long term IOM might very well be down to two carriers, Flybe for the trunk routes and Manx2 for the thinner routes.
I do not see VLM lasting forever on the LCY route, and Aer Arann's loyalty is also somewhat doubtful should they get under more overall pressure and cut back their operations. DUB would probably be sufficiently served by a Manx2-style operation anyway. And as for Blue Islands, not much difference whether they run a Jetstream to the C.I. or Manx2 a Metroliner.