This makes no sense and is a total misreading of the actual situation. It reminds me of the F-Line Magic Wand Theory, which is all of these projects would work great if we just had a magic wand to pass over them to solve all intractable problems.
Malvern St is useless for a connection. Extremely narrow and a right turn only just beyond the lights where Brighton and Comm Ave meet. ..... Regular vehicular traffic? Fuggedaboudit.
EDIT: One more thing. Malvern and Babcock are ground level streets that lead up to the railroad tracks. West station is going over the tracks, so I don't see how you can fit in a bridge/downgrade from West station and onto those two streets.
Magic Wand? We're talking about spending $1B+ to develop an area of vacant land that's the size of the Back Bay. And we're going to re-route a mainline interstate and multiple railroad lines in the same process.
With that level of investment, it's absurd to assume that existing conditions in the malvern / babcock area have to stay that way until the end of time.
How much would it cost to acquire the abutting parcels on malvern and or babcock and build a proper connection over the tracks? I can only guess...
....but is there any possibility that it's greater than $30m? We're talking about what....a dozen well-depreciated wood-frame rental properties, maybe some single-story retail, a parking lot and a softball field?
That's 3% of the total project cost, friends...
....and a fraction of what commonwealth is spending and will spend elsewhere to create or improve comparable cross-town connections. How much is being spent to replace the casey overpass @ forest hills? How much to redesign Morrisey blvd? How much to add a bus lane to Rutherford Ave. & the N. Washington St. Bridge? How much to ground McGrath in Somerville?
...and if you did it right you could tie-in some upzoning and other incentives, and everyone could be a winner. (And maybe pedestrianize harvard st., with a bus-only lane down the middle, but that's a different can of worms...)
Not taking this opportunity to dramatically improve the connectivity of the street, bus, and transit network is absurd and pathetic. (...and, with respect,
talking about the convenience of left hand turns from Malvern St. is missing the point by an order of magnitude)