Create plugin that writes fetch buffers to indexedDB or Cache so they can be quickly read from disk rather than waiting for data to fetch. Though this is possibly just bypassing the browser cache it's guaranteed to work even when the asset headers aren't set correctly.
Could reset on page load / unload or retain data between reloads. Possible to set a "time to live" on the cached data?
Other
Could increase queue size on initial load.
See skipping settings for cesium's tiles - current issues with the threshold setting means that when the the camera zooms out and parent tiles must load then the tiles "pop" to the parent LoDs.
Related to #529, #525, #490, #185