Official comment
This is not something we currently offer in MME. We already pre-trim the images around the flight envelope to get rid of jagged edges. We recommend doing further trimming with the raw GeoTiff files in QGIS by using its Raster -> Extraction -> clipper features.
You can also do some basic color corrections is QGIS.
We anticipate doing a few tutorials on this very soon.
Mapbox is geared towards people making maps, not necessarily developers but I get what you are saying. We will look into documenting some of these features a bit better soon.