Full disclaimer: I'm a Blender user, but I feel like MI users would benefit from this feature
OCIO is a open color standard that many pieces of software like Blender user. By adding OCIO support, a piece of software can get access to configurations like Filmic, ACES, AgX, etc, all without needing to add extra work (other then using the OCIO C++ library). It is an extremely powerful feature, and I feel like the MI community would benifit the most from it.
Most MI renders I see seem to have dynamic range issues that Blender's Filmic solves easily. If OCIO support was added and Filmic came bundled with MI (Filmic is open source and as far as I know there's no legal issues that would result from using it), this issue would be solved without users having to do anything extra. The same can be said for people wanting to use ACES. All they would need to do is install ACES (by putting it in a color space folder that MI could read when starting up) and boom, they're ready to use ACES (albeit with some workflow changes needed since ACES is a whole other ballgame). All that would need to be done on the development side is to add OCIO support. The possibilities are endless.
OCIO has its own documentation which can be found here: https://opencolorio.readthedocs.io/en/latest/guides/developing/developing.html