service is almost always busy in J and W, however the passenger profile is basically wealthy couples going on holiday, or couples who are treating themselves or are taking a special holiday for honeymoon/anniversary etc. I don't believe the route requires or could sustain an F cabin.
Any F demand for MLE
would, I believe be made up mainly from upgrades with miles etc not actually pax buying full price F tickets.
The other issue is that if you put a 4 class aircraft on the route you've then got a 4 class aircraft operating other routes from LGW
which are currently on a 3 class due to the fact that there isn't just one aircraft dedicated to MLE
Although I don't agree the route needs an F cabin, one thing I would say in favour of a 4 class aircraft is the config would suit the route better I think in terms of maximising revenue
Being configured 14/48/40/124 rather than the 3 class of either 0/48/24/203 or 0/40/24/216 would give BA
more W seats to sell which I think would be a good move on the MLE
route and the loss of M seats I think would be ok as the flight often has a fair number of M seats empty. You'd also have 48J all the time rather than only sometimes as the route is sometimes operated by a G-VIIx aircraft (although not often, usually a G-YMMx)