Mark,
I’m not a Motion whiz, so maybe better help on the Motion forum, but anyhow, this may be a retarded method but it would probably work. Put a retiming “set speed” behavior on the footage and set the speed to 100%. In the properties inspector twirl down the timing arrow, there are a boatload of setting you could try, including optical flow.
More I think on this, in FCP you could put a deinterlace filter on it, and depending on which one you use may get a few blendi9ng options, Fields Kit from revisioneffects.com would give you this.
Have a wonderful day.