Stobart has already admitted that Southend has limited expansion potential due to constraints not only physical but as laid out by Southend council. Stobart would need to diversify by buying other airports with borrowed money.
I would not be surprised that Stobart does not have a hidden agenda to sell the airport in maybe 2 to 5 years time. Nothing wrong with that but you only need to look at some of the airport owners in this country to see how things can take a turn for the worse under the wrong ownership.