I'm wondering whether in the near future support will be improved for styling basemaps created with proprietary, or non-ESRI, data. We are attempting to style our own data as basemaps but are running into a lot of missing holes in support for the Mapbox GL style spec.
Will there be better integration and support for what the style specification is for Mapbox tiles?
We are a little bit behind you in this process (trying to inject our vectors into esri's base-map vectors - successful in Pro not in ArcGIS online). But, has ESRI documented these holes or could you provide some specific examples where the style spec is lacking?