Ramp Rat mentioned Flybe earlier and they were one of my first thoughts - if you look at their network from LGW it is an excellent fit for STN.
Channel Islands aside, which I can't really see moving, none of the other routes are served from STN and BE do in fact have competition from EZY at LGW on a few of them (ABZ, IOM, INV). Add in the arrival of EI on the BHD route (a destination STN has recently lost) and LGW's recent dislike of smaller aircraft it becomes a nice rumour.