Lets get some sense of perspective here.
1) The runway, navigational facilities and infrastucture at Carlisle are in an extremely piss poor state. To cope with freight on a major scale the runway needs to be rebuilt and lengthened by 300m, not just resurfaced. New Lighting and an ILS would have to be installed, along with refurbishment and expansion of ground handling facilities, and , if you want pax operations, the terminal - a total bill of at least £25m or more.
2) There is insufficiant demand within the local catchment area for any scheduled passenger services from Carlisle, it doesn't take a brain surgeon to work out that despite Newcastle being 60 or so miles away, they'll always offer a better deal to anyone who wishes to travel to London, Europe or beyond.
There is now a reasonable, albeit expensive train service to London, and although quicker, there'd never be the financial justification for a scheduled service to London - even if it was to Heathrow or Gatwick for interline purposes.
All credit for Stobart's new owners for mooting the idea, but I doubt they'd be able to raise or justify the investment to bring the place up to a standard where potential freight or passenger airlines would even look at the place.