Thank you for sharing your approach for WebP! I have created a tool to convert to WebP format.
To use it, simply execute playcanvas-cli webp or npx playcanvas-tools webp in the downloaded project. This will create a config_webp.json file (if using the default settings), which you can then add to the __settings.js__ file by specifying the new path.
After using this tool on the entire project, the 33.29MB texture was reduced to approximately 3.55MB (89%). While I believe that further testing is necessary before using this tool in production, I found it to be very effective.
Repository: GitHub - yushimatenjin/playcanvas-cli: The PlayCanvas Command Line Tools.