A few things to keep in mind - most people already know most of this, but it's good context.
NYCFC was very close on this site before. In 2013, there were plans to build a stadium there, with a size reported to be 25,000 - 30,000 - the NY Post said 28,000. So, the work has been done to figure out whether we can build there and how large. The NY Times reported that 153rd street would close and that the exit ramp off the Degan would have to be moved.
The street where Rupert Plaza Garage exits is at the end of 153rd, but it is technically 157th street. My guess is that it would not have to be closed.
Further, you will see on some maps that "157th Street" runs in between the parking garage and Heritage Field Park. In reality, that is where 157th Street used to be, but now it is just a walkway. I would imagine that any Stadium project would involve expanding that a bit into a larger pedestrian plaza. Next to it is a part of Heritage Field Park that is now just underused green space and walkways. It could presumably be used to expand a plaza area, although that would doubtless be controversial.
The train station is an impediment, but there are ways to make it work. The tracks and platforms are already very low, and it should be easy to at least have an upper deck fly some distance out over the tracks, assuming the MTA will agree.
The bridge that runs from the train station to Heritage Field Park is just to get pedestrians over the GAL factory and parking lot. If our Stadium is there, it wouldn't be necessary, as you could have pedestrians exit onto whatever plaza takes the place of that parking lot.
The iconic bat that used to sit near the main entrance to the old Yankee Stadium now sits at the exit to that pedestrian bridge. Preserving that might be a challenge.
https://nypost.com/2013/12/10/bronx-scores-400m-soccer-stadium/
https://www.nytimes.com/2013/08/30/...al-would-give-the-yankees-a-new-neighbor.html