My experience with converting JavaFX 10 to 11, even with the small programs I converted, is that it is a non-trivial process. I made the decision to use Maven to control the execution and dependencies.
Still, there are some really good things that have already come out of the switch. The big one for me was that FXML files can now actually be in packages of their own. Pre-11 they had to be in the same package as the controller.
You can see what I've done with my bindings demo
here. The master branch is JavaFX 11 and pre-javafx-11 is... well... pre JavaFX 11.