I've been using mixed playlists for awhile now. I'm thinking it was a vid I posted you watched :)
Surprised there's not more talk about it around the forums.
I still don't understand why the programmers don't implement this into RB. I understand that some people will have exporting issues ( possibly - if their MP4 are from shady sources ) but IMO if someone is using the video plugin they are 99% laptop / controller DJ. A simple check box to allow mixed media for those of us who could benefit
for now - I'll just continue loading my MP4 in 4.0 and playing in 5.3!!