I take the day flight from BOS-LHR at least once a month. There are devotees of that flight who take it whenever possible (jetlag is really minimized). I used to be able to take it and then switch to Paris that evening but then the last flight out to Paris was cancelled. I still take the day flight when going to FRA or ZRH then next morning (staying overnight at the Sofitel).

I'd be a regular on a day flight to DUB and that would allow me to connect on connect onward that evening (I usually fly BA F, and it looks like Aer Lingus only has business class, but I'd tough it out). If it left at 8 AM from BOS like the BA flight, it would arrive at 7 PM and one might be able to make 8:30 PM or 9 PM flights to various places.

Do you think there would be sufficient interest in morning flights from the US to DUB? Or, would BA worry about the competition to the flight to LHR?