The way I stumbled upon to get retiming behaviors to attach inside a motion effect template, was to import any video clip, attach retiming behavior, make it a dropzone then clear the media from the dropzone.
It then publishes fine, but apply the effect in X and you get an instant crash.
I tried publishing it with a 1frame media clip hoping you could just clear the dropzone in x, but to no avail.
Retiming behaviors being available in x would be helpful in soo many ways.
Cheers,
Bg