A route to Heathrow with onward connections would certainly be viable.
Euroair, probably other(s) also, operated a LHR route in the good old days and failed, it needs to be operated by an operator with interline connections whereas, in one booking, they can book CAX/DXB or wherever and not pat thru the nose for a CAX/LHR and with no guarantee of making their onward connection that they may have paid again thru the nose for.
But then Stobart Air don't wish for a LHR service ... They seem to only recognise one LON airport!