Would love for Plex to support Pegasys Inc.'s .pgmx format. This format/container can playback as a regular full Blu-Ray complete with menus. Since Plex does not support ISO’s, this could be a better option.
Currently the only way to play this file format is with Pegasys’ own player. The format also can only be created with their PGMX Creator software. The creator software is pretty cheap at $40. Player software they give away for free (not open source).
I’d be shocked if they weren’t willing to license the format since they would have a financial gain if more players supported it.
Here is a link to their website and software products:
PGMX Creator: TMPGEnc PGMX™ CREATOR - Video, Subtitles, Slideshows and Menus, all in one file.
PGMX Player: TMPGEnc PGMX™ PLAYER - Free PGMX video player software