I think Stobarts intentions at CAX are twofold, with the main one being the construction of a new HQ and warehouse on the airfield and it is only that which has needed, and was recently given, planning approval.
As far as the airfield itself is concerned they seem to have reduced their aims to resurfacing the runway and converting a recently built hangar into a passenger terminal. In other words, they will do just sufficient to enable the establishment of a passenger service to London, with SEN as the destination, which seems to be one of their main ambitions for CAX in the short term.
As far as the station at SEN is concerned, all I can say is that Alastair Welch (who is no fool) sees it as being the key to future success in attracting passenger services. If a CAX-SEN schedule is established, either under Stobart livery or by another operator, it could well act as a catalyst to demonstrate SEN's ability to serve London. After all, the transit times from touchdown to arrival in central London by train will be virtually identical for SEN, STN and LTN so I cannot agree with the "red herring" comments.