I'm not following the issue? do you want to use full screen in other places besides templates? or use the templates with full screen but in some other cases?

I'm assuming you want to reuse ACE (maybe also check if it needs upgrading) in other places besides templates?

I want to decouple the full screen button from the ace editor so that any element can be made full-screen (for example, for expanding text fields for #3856).
The goal is to have a sort of "fullscreen-button" helper that will let you make any given element display full screen (might be other uses for this to, for example host console)