My vision is that ideally VE standalone would work in mobile on it's own, and so the MW integration would be as light as possible: connecting up the load/save APIs and placing the VE instance in the right place.
Converting MF to OOUI widgets is also a great goal, and will make moving code between the the extensions a lot easier.
I'm CCing in Bartosz as he's doing great work on OOUI at the moment, and it would be great if he could work with mobile to make sure we have all the widgets and browser support tricks we need for touch devices.
Ideally all the existing code should live in VisualEditor and be based
on OOJS UI. In the future we could also imagine the wikitext editor in
mobile becoming part of the VisualEditor tool itself.