Build the isolated Light Rail line/GLX up the existing Bikeway ROE and replace the Bikeway with a dedicated, curb-separated bike lane running up Mass Ave from Lexington Center to Arlington Center, and have the light rail run down a Comm Ave-style median ROW from Arlington Center to Alewife Brook Parkway where it would hang a right and follow the Brook to Alewife like the D Line uses the arborway from Fenway to Brookline Village.
That, or build it like the Hunt Valley extension of the Baltimore Light Rail and run the the light rail service on a single-tracked ROW with passing loops in the places where the Minuteman parcel can't accommodate two tracks and a bike lane, prioritizing traffic in the direction of commuter flow during rush hour.
That, or build it like the Hunt Valley extension of the Baltimore Light Rail and run the the light rail service on a single-tracked ROW with passing loops in the places where the Minuteman parcel can't accommodate two tracks and a bike lane, prioritizing traffic in the direction of commuter flow during rush hour.