Dynamically fetching from multiple tiles files

[nigelsim]

We currently have set of layers on MapBox that is served by a source that is dynamically selected by the UI (URL pattern generation), basically, because the data comes from different sources for different areas, and has different update cadences, so our pipeline pops out one MBTiles file per original source.

However, we're now getting situations where some features could be visible at the same time as others, so we are revisiting our approach.

Once solution, similar to how mapbox:// paths work, would be to have a way of selecting multiple source tilesets to be combined into a single request.

e.g., if you had a config of

{
  "data": {
    "AUS": {
      "mbtiles": "tiles/AUS.mbtiles"
    },
    "AUT": {
      "mbtiles": "tiles/AUT.mbtiles"
    }
  }
}

You could request http://tileserver/data/AUS/{z}/{x}/{y}.pbf or http://tileserver/data/AUT/{z}/{x}/{y}.pbf to get the individual tiles, or http://tileserver/data/AUS,AUT/{z}/{x}/{y}.pbf to get a combined set (merging layer sources together).

Is this a bad idea? Would it be hard to achieve in the current architecture?