I think they could build up a nice airport there with right investment
There lies the problem. Who is going to invest in it? If you think Sutton Harbour - your wrong. They are only interested in safe, secure investments - not airports. What happens to the ASW routes at NQY when Easy and Ryanair pop a shiny A319 or B737 on it??
There are a heap of potential routes at BRS, but alas no business sense to set any of them up.