> In terms of classloader separation, I don't know OpenLiberty at all, but isn't there a way to add modules to the server itself?

There isn't any way that a user can add modules to the server which are read by official server modules.

> Like common libraries you'd like to share across all deployments? This used to be possible for all the common servers at least back in the day.

We can add JavaFX as a common library so that the application classloader can get at the classes, but this won't expose the javafx packages to the server runtime (where the builtin JavaFX validators live) for the same reason as above.

NOTE: I was finally able to get these tests passing by adding javafx.* classes to the boot delegation list in the OpenLiberty kernel. However, I'd rather not make that change and would prefer we exclude these tests for Java EE environments.

> It'd be nice to explore this route before we commit to excluding these tests (at least by default). I'd strongly prefer the TCK to be as extensive as possible.

I'm not proposing that we exclude these tests by default. Rather, I suggest that we exclude them for the Java EE (i.e. "incontainer") profile of the TCK.
In my mind, there are three classifications of BeanVal 2.0 environments:

1) Java SE
2) JavaFX (JavaSE + JavaFX)
3) JavaEE (JavaSE + JavaEE)

Any tests for Java EE would not be required to work in a JavaSE or JavaFX environment, so likewise I would not expect JavaFX tests to be required to work in a JavaEE environment, since nothing else in JavaEE has a dependency on JavaFX to date.