It would be nice to have a name that was unique, like OpenEXR is. ¬†Other names that popped into my head early on include OpenMovie and OpenMOV, maybe using the .omv extension. ¬†UMF isn't bad. ¬†Obviously POM is what I'm still favoring.
It was also pointed out to me that what I'm proposing to do is similar to these MXF "Application Specifications":