Ratger, why didn’t BA offer it? It’s for the airline to resolve their overbooking mess not for the victim of the downgrade to find a creative solution.

i disagree with your second paragraph, delay/cancellation compensation is not linked to class of travel so if ba can fly a passenger without delay (but downgraded) or offer an alternative flight (but in the original class) and the passenger prefers the latter, ba would undoubtedly view this as a voluntary change so no compensation would be offered and I’m minded to think that cedr would likely side with the airline on that interpretation (courts might or might not be a better pick).

And that’s of course before even considering that to jfk, an alternative flight arriving with less than 3hrs delay is quite likely given schedule density.