Whilst I don't argue the overall thrust of their letter, yet again they use false arguments to try and persuade.
What use is a carrier with GA jets but no AD? Bring back GR9 by all means, but without FA2 it will be too vulnerable and that would compromise tactical usage.
Harrier more advanced than GR4? Wrong! Could Harrier carry DMS Brimstone or RAPTOR (CAS is not the sole required role)? Could Harrier operate in ALL weather (ie low level too)? Did Harrier have the range/payload capability? 2 heads vs one in the cockpit. Could we afford to dump all those expensive weapons in the sea due to poor bringback capability?
Don't mean to turn this into GR9 vs GR4 again as it has been pretty much done to death, but if they got their arguments right in the first place, they wouldn't need to be corrected!