I have been following this purpose since years now. The fact is Mycroft stops “hearing” if there is a significative pause, so we need to find a way to do it properly. Besides that difficulty, I don’t really know how can Mycroft can entirely replace the keyboard and “be aware” in which application it needs to behave as a keyboard (libreoffice document, notepad, or a simple textbox on any application), I guess that will be very difficult and you’ll need to go deep into each desktop environment to obtain where the cursor is focused at that moment.
@JarbasAl did years ago a dictation-skill (deprecated, not for use, not maintained and unsupported, so no need to ask him for help as he stated this skill is not for use), but you can take a look into it if you want some inspiration.
I did rummaged with pyUNO, the Open|LibreOffice API, and perhaps we can do something in this way, just with the libreoffice|openoffice suite.
I’m very interested in this subject, but I think this is a very big project, and if it is even possible, you’ll need the help from the Mycroft devs themselves, for the reasons I said before.