Thanks Jay, you are correct that MMPKs are supported in Pro 1.3. They are actually supported in Pro 1.2 as well, and any version after that. You are also correct that Navigator for ArcGIS 2.0 or later now supports the use of custom MMPKs.
I'm wondering, what took between 9 and 33 hours? Just running the Create Mobile Map Package geoprocessing tool? Or the whole process of making an MMPK, from start to finish?