Thought I'd wade into this one being a bit of a NYC route user.
a) Had a good friend travel CO from LGW and thought they were pretty awful. I think what upset him was the 50p nominal charge for the headset! Well something along those lines, terribly infra dig.
b) c) Restoring the LGW-JFK route might avoid the 'bun fight' at Terminal 4 when departing our green and pleasant land.
d) Going to Newark has got to be better than 'running the gaunlet' in getting to and from JFK. Had the odd bad public transportation nightmare journey in this respect. Heard the new transit link from EWR is pretty good. No changes, etc?
I think half the problem is, if I recall correctly, is that some of the flights from LHR departed slightly earlier than the Gatwick one.
This gave more time at the arrival destination and more flexibility to the infamous Business Traveller.
Hope this helps.