It looks like a slight adjustment to the plone.formwidget.namedfile might make it possible to ship Plone with seekable/skippable media files.
Once a playable file gets longer than 30 seconds it becomes frustrating to be forced to "endure" an entire video or audio clip when the user only wants to find a 10 second part near the end.
A small change, borrowed from ideas in wildcard.media makes it slightly easier to provide seekable/skippable media files.
I've added an issue:
A stretch goal would be to provide an embedded player out of the box for any file that is detected to be audio or video.