To further this, I'll do another texture usage flags optimisation pass after other issues have been fixed. Using staging textures is a catch-all for all compatibility paths, but it is not the most optimal. For cases where textures will be updated frequently, it is more efficient for these textures to have write support and to be updated directly.
The motivation for avoiding the SHADER_USAGE_WRITE flag is that it disables lossless compression, which will reduce sampling performance. However, this is primarily beneficial for render targets, which are updated within the fragment shading pass. As opposed to all textures.