Here is something I don't think I have seen discussed here yet. I don't really think this is a super crazy idea, but, I guess for the MBTA it might be. So, I was thinking about how to add capacity (while almost being crushed to death @ DTX) and I thought of the Red Line being lengthened back when the Braintree line was added. It seems like that wouldn't be very easy to do again on the Red Line (considering the half ass job they did the first time for many of the underground stations), but I started to look at the Orange, and it seems like it wouldn't be too terrible to add platform length on most of the line. I realize the new rolling stock will provide better head ways/capacity, and things like extending it also need to happen, but it seemed like a reasonable idea to think they could also lengthen the trains.
It looks like pretty much every station south of Tufts would be easy enough to extend the platforms for - basically any station in the Southwest Corridor. It also looks like (from basically Google Maps aerial views) it extending platforms on stations north of North Station would also be fairly straightforward. That would leave just six (out of 20) stations that would probably be fairly coplex: North Station, Haymarket, State, DTX, Chinatown, and Tufts. Does anyone know if it would be feasible to extend the platforms in these stations? I would expect anything in the Washington St Tunnel to be the worst. Even Half platform stub ends (like the Red Line extension) would probably be OK, but not ideal.
I would think adding enough platform space for even one more pair (2 cars), assuming more rolling stock is purchased to accommodate this, along with the improvements the new rolling stock is bringing (including more sets to run better frequencies) would really go a long way in reducing current and future congestion on the Orange Line.