I heard that a CRJ-900 operator had been in talks with BFS recently. Air Nostrum (Iberia) operate a sizeable fleet from MAD and they have operated seasonal flights from other regional airports in recent years.
Remember Air Europa operated a weekly charter with inbound tourists to NI a few Summers ago which were usually full. A MAD service wouldn't beyond possibility.
The only factor that would effect the possibility of a service from BFS is BA/ IAG operated from BHD.