Booked a RT itinerary leaving Boston on a Wednesday and returning to Boston on Saturday (both flights non-stop), but something came up and I need to be in New York on Saturday night.

Instead of booking a train or another flight from Boston to NY as soon as my original flight gets in, I was wondering whether it's possible to use JetBlue's $50 same-day change fee to choose one of many alternate flights that connect in New York on the way to Boston, and just hop off in New York (I will have no bags)? Or does the routing on a same-day change need to be exactly the same as the original? And if the flight via New York leaves earlier than the non-stop to Boston, any way I can standby for free if I acknowledge to them that I'm OK with the (wanted) "risk" of being stranded in NY?