Welcome to the board, ypd; good to see more guys otj. I live within the 4th, and work in a small PD about 10 min away.
I only have one boat on Kensico, but like you said, several of the guys here share several boats on different reservoirs. Getting to the DEP boat auction may benefit you, and you may able to pick up another boat to have access to a res more known for trout.
Regarding trout in New Croton: weirder, unexpected things have made it into local waters....like huge striped bass out of that same reservoir. Just because it's not listed as a resident species does not mean there are none in there. I've caught perch out of old, flooded iron ore mines before. I have NO IDEA how they ended up there....but it did provide about 2 hours of fun once we found em lol.
I couldn't help you with muskies. Being I came from farther up north before moving here, the only tiger muskies I've seen have been pulled out of Greenwood Lake.