The Sea Harrier FA2 was a fighter / interceptor, weapon range in the order of 50 miles, the GR7-9 is a bomber with limited air to air self defence ability range 1-4 miles depending on one's luck.
As mentioned previously, the 'improved aerodynamics' include going 100mph slower; but it is a fair bit more user-friendly.
I agree if we had to bin the Sea Harrier, ( which we didn't ) a sensible move would have been to get some Harrier 2+, as while it IS beefed up, it does have a lot of commonality with the GR5,7,9.
Like everyone else I'd normally jump through hoops for the chance of a Lancaster flight, but if over Afghanistan etc maybe not...and what's this about a ventral gun - did someone cut a hole and poke a Bren through ?!