Ok, but since the area of 79th and York does need a new station (as @Wallyhorse has said), here’s my plan:
So maybe run the up 21st to Broadway, then across on Broadway (with Stations at 11th St, North Roosevelt Island and York Av/82nd, then curving up to 86th to meet up with SAS. At the end of the line, After a stop at Central Park West, to connect with the , the Would run (with a stop at 91st/Columbus), with a connection to . Maybe in a later rendition we could have a branch going up Columbus (stops at 99 and 106) to 110 then connecting to the at 110.
Thoughts?
PS: more than half of 102 Street doesn’t exist - it also doesn’t exist between Manhattan Av and Amsterdam Av