NCL-ARN is double the distance of MAN-CDG, just short of 800 miles in a Dash 8. While i'm sure it's possible, I would be happy to bet £10 Flybe won't do it. It would make just as much money, if not more by going to Belfast twice in the same amount of time.
Not with the present loads to BHD it wouldn't.
Distance comparable to BHX-PGF which was a perfectly acceptable and very well-used Q400 route. And FSI have a Q400 sim in ARN - always handy to have a direct company route for any period the Farnborough facilities are maxed out/tech.