Yeah, what I ended up doing is a little bit differently.
I overrode the functionality in the currently existing Compile
class like so:
Defined a new class that extends CompilerInstructionsBuilder
that does not call addMainClass()
Defined a new class that extends Mxmlc that uses that
Defined a new class that extends Compile that overrides
createDelegate to return the new Mxmlc extended class
Seems to work pretty well, I'd love if this functionality was
added to Gradlefx, but for now, this works for me.