I actually have a plan for a Staten Island subway. It involves an extension of the IND Culver line under Fort Hamilton Parkway/10th Avenue, as a 4 track line. In addition to this plan, it involves a new BMT Interborough line under 67th Street and along the LIRR Bay Ridge Branch right of way, as a 2 track line. Furthermore, two branches of the BMT 4th Avenue line will branch off. One of them involves an extension south of the Bay-Ridge 95th Street station which will then run under the Narrows, while other will branch off at 59th Street by utilizing the unfinished 67th Street tunnel meeting with the proposed BMT Interborough line. By "meeting", I meant that there will be a total of 4 tracks with no merging involved. Anyways, here's my take on how the NYC subway system should expand it's subway system including Staten Island: Revolutionary New York City subway map
https://goo.gl/maps/gh1xdw1BFb1kGKDq9
If you have any comments, questions, or concerns, let me know.