Correct, not a viable passenger airport, or should that be not a viable stand-alone passenger airport?
The first thing that it would need is a route, served 12 times weekly, morning/evening Sunday evening thru Saturday morning, to an international hub, AMS wouldn't be viable unless on a codeshare with KLM which wouldn't be likely as KLM are already serving all airports, NCL, MME, GLA, LBA & MAN, surrounding CAX.
The only London airport that may be viable is LHR because some 50% of the passengers would not be destination London but destination international, Carlisle to London/Euston might be just 3.5 hours by train but Carlisle to Heathrow is some 4.75 hours and includes 2 changes and walks up/down escalators of 5 or 10 minutes each, complete with suitcases etc. Across the Irish Sea, both BHD & DUB, did appear to be settling nicely in to a viable schedule when operated previously, then there is the opportunity for summer weekend flights, Channel Islands, Ireland or wherever.
I understand that CAX had quite a thriving flying club activity until the current owners urinated them off, well what better opportunity for new owners to either develop their own flying club business, across the old side of the airfield, and/or encourage the ex residents to return. Reading thru private pilot threads much of the time they are discussing which airfields offer the better deals along with the better grub, trainee pilots need x-country's as part of their training, other pilots need to build up hours just to qualify for a commercial licence, make the landing/navigation fees attractive along with a talked-about flying club cafe/bar and the business shall surely come in.
Encourage an on-site maintenance facility with attractive ground rent charges, it doesn't matter if it may be for choppers, light twins or whatever, it shall bring aircraft movements, landing/navigation charges, fuel etc., in.
CAX has the RAF Spadeadam training range as a neighbour, CAX has benefited from military movements previously, market the MoD to come in for refuels, landing/navigation charges, fuel, perhaps overnight parking, and these military types aren't proud, if the grub is good they'll be in the flying club for their pie & chips or whatever and the word shall spread amongst the squadron(s), they'll all be coming in there!
And should the new owners have their own in-house airline, and particularly once any franchise contract in Ireland may be completed, where more appropriate that they base their airline and maintenance facility than at their own in-house airport?
And what about the darn great on-site 'Stobart Group' warehouse facility, I'd imagine that the ground rent alone for that would be quite significant.
There's money to be made in them there hills, perhaps not in great abundance but money to be made all the same.