The big problem that HUY would have in letting a low cost operator in would be that it would almost ineviatebly be only on the Amsterdam service, and although this would be good news for some of the passengers, it would be very inconvenient for the majority because there would be no onward interline facility.
Since KLM pulled the Stansted - AMS service, we've seen a significant number of passengers coming up from the Stansted catchment area to use the NWI - AMS KLM flights purely because they can interline onward with no hassle.
Low cost is great if you have nowhere else to go.