DC3 - I'm not sure I follow your argument. You seem to be saying that you believe the number of people flying is likely to reduce significantly, at least in the short term. You seem to also say that being adaptable is also a good thing as it allows one to survive better when circumstances change
It seems highly likely that other airports in the south east of the UK will also be willing to change their business model given a significant reduction of pax flights
Why would Southend have an advantage over these other airports ?
AFAIK, Southend doesn't have a significant cargo capacity of which it can make greater use. It seems unlikely that PPL numbers in Essex will grow significantly. Southend doesn't have a suitable climate for aircraft storage. I doubt that SEN will become a major airline engineering base. Military/emergency services use of SEN seems unlikely to grow. Anyone heading to London in a private jet presumably has their eye on London City
Southend in the last few years has functioned pretty much as London's overflow airport - seeing growth because London's 5 other larger pax airports were pretty full (at least at peak times) and SEN could also offer pax a more pleasant experience.
How does being SEN being adaptable give it any particular advantages or sizeable niches which other airports won't also be targetting ? I just can't see Felixstowe, Tilbury and their ilk having a big increase in the need for air charters