we have been working with Cesium to provide a Client access to GeoJSON vector Tiles (OSMBuildings and Geoserver Vector tiles TMS), but for us it was impossible to do it using a Cesium native Classes, then we reused some source code of other projects, for example mbtiles to develop another solution with the same architecture but using tiles in GeoJSON format instead of mbtiles.
The result, in my opinion is awesome, because we can see OSM buildings in 3D (all World) in Cesium interface with similar (but not iqual) performace as Cesium 3dTiles.
we have tryied to do the same using QuadTreeTileprovider class but it is not running correctly because the workflow of the lastests release of Cesium avoid the use of this class with our needs.
for us is a bit complicated to mantain this custom source code, and we think that it is very important to provide this kind of capabilities in Cesium (interoperability), maybe it is already developed and we could not find it...
Could you help me to find a more CESIUM standard solution of a Tile Grid client provider to load Vector tiles or custom WebRequest?