I made a quick mockup of what it would look like in action, http://i.imgur.com/UD7MOFS.png

And I don't know if it'd be feasible at all but it'd also be nice if it could work with ALT view enabled with all factories currently on screen ( train cameras can kind of do that, but I guess there's a little bit of a difference on normal rendering and map rendering )

That feature is unfortunately not possible with Factorio's current GUI system, and even though the current GUI system isn't great and will be improved in the future, I doubt that your suggestion will ever be possible to mod in.