Considering the limited schedule to New London itself, a limited schedule east of there should be a-okay. I really wonder where they're going to lay up trainsets, though; realistically you need to have a set or two on the east end so you don't need to deadhead from New Haven to Westerly daily.
You'd very much want to have a stop in Stonington (Borough), as well. The population is dense in that area, easily within walking or biking distance. Later on you might want to have one in between Noank and Groton Long Point, as well. Dunno where you'd put a stop in Groton (City), though, the terrain the Shore Line cuts through there isn't exactly what you'd call "flat". The connections to the lower half of the City of Groton is abysmal from coming from New London via public transportation, though; when I tried commuting in to UCONN @ Avery Point for a couple of days via SLE and the busses, and it took me about an hour flat to get between there and New London Union Station.
But yeah, the devil is in the bridges... it's always the bridges, and that's what it all rests on. SLE has turned out incredibly well for demand for service, much better than could be asked for ( basically 25 years of non-negligible growth in ridership). I don't know how the ratio of dollars-in from the State to dollars-out (revenue), but it has to be pretty good. But it's going to be a hell of a job trying to court all of the parties on the bridges is going to be a hell of a job; Amtrak, USCG, Maritime Trade Association... maybe the U.S. Navy for the Thames River Bridge?
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