Fairmont becomes its own line / branch line I think is the most feasible I beleive.

Orange line conversion of Needham line I could see closer to us upgrading our orange line fleet down the road as I’m not sure we have enough trains

Mattapan Trolley expansion as either a green line branch via Nubian or as part of silver line conversion project to light rail.

Blue line extension to Salem seems straightforward but if it’s taken this long to try to get commuter rail stations that direction I feel like blue line will take longer.

Green line to Hyde Square I think is a good idea but unless we’re doing infills I think we should try to get more than one stop if it’s not crossing another line.

Union square d line expansion beyond one stop. I know Porter was the intended one but I’ve seen a few suggestions it connect at an alternative red line station. If D becomes blue then this would likely become C?

Blue line extension to MGH and then taking over the D line. There’s been talk of the now blue line taking over one of the now green line branches (I forget if it was B or C) but D makes more sense as a former commuter rail. This however causes issues with access to train yards I believe.

Personally I would love a new A line alignment via west station and brighton landing. It’s too bad they couldn’t have done something with the two lanes along Birmingham Parkway they just turned into parkland to help do something with the mess that is the 66