I became interested in this because a test failed, so I can stop when it is deemed right to do so. That said:
The current methods calling the methods you mention will look very weird without the ExternalForm loaded. There are branches that make no sense with that package removed. I did 3+ years from now if someone needs to work on Form and especially those methods they might be tempted to just remove them and then we are much worse off.
What I'm suggesting is to factor out ExternalForm versions of those methods into ExternalForm and ExternalScreen where they will make sense to someone looking over it in the future. In the process the methods in Form should also get simple and more understandable (although there is a lot of but twiddling left in them). As a bonus I would leave a note in the Form comment about the existence of ExternalForm in case someone was looking for such a thing.
Yes this approach can also for over time - but at least ExternalForm will be consistent with itself. And it might not for as fast asvleaving the mixed methods in there now. The only good way not to for is to put the classes back in, really.
Thanks,
cbc