As an observer of the many lows and few highs of HUY for over 35 years I can only hope the airport owners have a business plan not to compete wih DSA but to compliement it.
My observations over the years is that HUY is not sustainable by relying on scheduled flights, as pereviously mentioned on this and other threads, there is just not a big enough catchment area to attract both regional and low cost operators to the airport.
As for the engineering hangar, it seems this could attract further traffic to the airport but as previously stated, whom would use the hangar regularly to make this a feasible option. I presume Eastern have their own maintainence hangar at the airport and would'nt contract out their work.
The current chairman of Eastern, then owner of the original Eastern back in the 80's made public his intentions to start an express package handling centre at the airport but this never came to anything. But on that thought, would HUY be a cheaper option than flying freight into the main airports then distributing said freight via the good motorway connections from the M180. Probably not pratical but just a thought!