I personally don't think Millerton could be feasible without taking up the Trail. The cuts and line-side homes get pretty cozy to the ROW, especially as you get closer and into Millerton. Plus there'd be no way to return to the former station site without doing some major redevelopment; you'd either have to have a new station built south or further north of the former site without completely throwing things into disarray.
I'm usually through Millerton two or three times a week at least, and regular weekday traffic from the locals certainly doesn't warrant rail service. Friday - Sunday can get pretty busy at times with the people who come up from the City, especially in the warmer weather and when there's an event in town, but again, nothing too extreme and usually pretty central to the section of 44 between the two traffic lights.
What Millerton would really benefit from would be a dedicated municipal parking area to get cars off the side of the street, which is really what gets annoying. There's no worse feeling than when someone's parallel parked three feet away from the curb and you meet a tractor-trailer coming the other way, haha. Plus I can't begin to tell you how many times I've seen people just swing their doors open without looking at the road.
If the MTA were to invest in Millerton, I think the best option would be to create a municipal parking lot with a dedicated shuttle bus to/from Wassaic. That right there would alleviate a huge portion of the congestion in town and require far less resources than extending train service.
While we're on the Beacon Line thread, whatever became of that whole ordeal with the MTA seeking proposals for the line a while back?
"That sapling that once grew just south of Wassaic may be long gone, and the Harlem Line’s appearance may have changed over the years, but for decades to come, I can count on it continuing to provide me with funny recollections"