I think Nil Further is closest to the truth. To order a bunch of jets, you have to prove financial fitness to the manufacturer, and that normally involves having tens of millions in the bank. I believe the figure for the RJX order was 8 million, and that was a few years ago now.
Of course if you are leasing it is a slightly different picture, but you still need cash reserves. Flybe may be in better shape than years gone by, but they don't have significant cash reserves -yet.
I hope they stick with the 146's until a decent replacement is found, and not order any more of those god-awful Q400's. As mentioned earlier, Bombardier were desperate to sell some of the Q400's and I imagine there were very deep discounts.
As far as the RJ's are concerned, any heavy maintenance will be BAe's call, not flybe's. They had similar issues with the Thai 146-300's, as the Thais had not bothered to do the proper biobore treatments that prevent this sort of corrosion. I also find it hard to believe they would paint them before ripping them to bits - makes no sense at all.