Crewmeal - re BHX-BLL
There is a lot more to Billund than Legoland and scenery. Lots of business/industrial synergies with UK. Why do you think it has maintained a LCY link for so long? I'm sure it was served from BHX before, certainly it is/was from MAN.
It is exactly the sort of route that should have worked; if it doesn't, well then you have a problem because it suggests companies aren't willing to pay the fares required to make routes too thin for LCCs work in enough numbers. You would be looking to draw in from a wide area for such routes, and it looks as though some of that market have probably gone for the low fares of Ryanair from STN.