After publishing my proposal for subway expansion, I received feedback on the plan. Some of it was constructive, and got me thinking, so I revised the proposal in order to improve it. Most of the adjustments were in the Bronx, but there were some small ones in Queens as well.
In the Bronx, the (A) is curtailed to Fordham Plaza, where a convenient cross-platform interchange would be built. The (A) to Bay Plaza would add way too much mileage to the longest route in the system, and if the transfer is convenient enough, it would be just as good as one continuous Pelham Pkwy/Fordham Road Line.
The second part of the revision is a link from 145 St on the Lenox Avenue Line to 161 St – Yankee Stadium on the Jerome Avenue Line. Something like this was actually planned in the early days of the TA using the former 9th Av Elevated ROW. As part of this, 148 St would be closed, also providing a future possible home for the Transit Museum. This would allow for the doubling of Jerome Avenue service, allowing Jerome Av peak express services while also reducing transfer volume at 149 St – Grand Concourse. The boosting of this service would provide more service to the corridor and points west, thus reducing the need for a University or Sedgwick Avenue Line.
As noted by vanshnookenragen, it would be significantly easier to make a 73 Av Line via the Jamaica Yard. This has been depicted in the map shown, although I have my doubts about whether or not you could do it without significantly harming yard operations. The 73 Av Line is also extended two stops east, to Francis Lewis Blvd and Springfield Blvd. Francis Lewis Blvd is definitely a worthy terminal stop; the cost-benefit of Springfield Blvd station (or Bell Blvd instead, which is denser but has poorer bus connections) is dubious given the very low-density nature of the neighborhood. However, the relatively close distance of Union Tpke and the overcrowded Q46 ensures at least some level of high ridership, and it is also a faster trip to take a train from Springfield/73 to Forest Hills than to take the bus to Springfield/Hillside and the train from there due to the wider stop spacing and the lack of stops between Main St/73 Av and Forest Hills.