I have proposed a Queens TramLink system as a joint effort with @Jova42R. Please see the link below for the proposal.
https://docs.google.com/document/d/1xz17-KIFRDWieUCrQZo82xELDbdi0dx9dW3r2wNo31g/edit#heading=h.5b9dlcng3cvk
Another suggestion I have would be to have a light rail line as a shuttle between the airport terminals at LGA as there is currently no AirTrain serving this route.
A light rail sounds like a cool idea for NYC. However, I would recommend using Kawasaki LRVs as seen in Philadelphia so there's the option to run it as a single unit if necessary.