I know the new connector is the part we haven't been discussing since the United/Continental merger, but the bigger part of the announcement is really the confirmation of what would amount to a whole new terminal at most airports. 25 check-in counters, security check, 8 gates, though those might just be existing ones in the 2 sides which will be rearranged to work with the newly position entrance...
I think that in designing this thing, Massport would do well to look north to Portland's new terminal. It's a similar project - adding new check-in space, security, and gates on to an existing and limited old-style terminal building. Portland's strategy (security built above, removing the need to waste front-to-back space in the narrow footprint) would work pretty well here and would give an opportunity for more of those glass curtain walls airports seem to love so much these days. You could build a new food court up there too and leave almost the full width of the departures level for expanded gate areas. Bust out the roof of the old building and double the roof height, while having security-level walkways hung over the gates below. It could look really great.
The CE connector is entirely designed for JetBlue. No other airline really does international feed through Boston. AA and Delta do a little bit, but they prefer to use JFK.