Short update after 1.5 month of silence:

I have been working all this time on importing the planet into Mapbox GL format to offer offline support for this widget. Turned out to be a major undertaking due to the lack or scattered documentation, rather sub-optimal import tools and large CPU requirements. After struggling with the available tools/scripts, I ended up writing my own on the basis of OpenMapTiles schema: https://github.com/rinigus/mapbox-gl-importer

As it is, the planet got imported yesterday night and I can confidently say that the offline support for Mapbox GL tiles is coming as well via OSM Scout Server. There is still some code to be written, but I don't foresee any blocking issues on the way.

As for vector tile schema, it will probably change in time. Already now there are slight deviations from OpenMapTiles schema to optimize import and I can see that few POIs are missing on the maps. I will document all the differences in due time. Most probably we will optimize the schema in time for our needs.