Deferred thumbnail generation would be a huge improvement and would put an argument of bloated uploads dir on the sidelines for webp co-generation. I would happily take a penalty of loading full image util the thumbnail is ready just to have that benefit but further optimisation could be made to always create a 1024×1024 (or other size) to be used when a small thumbnail is requested and its not yet available to make this less of an issue.

Over the years I’ve tried bunch of band aid fixes for image problem, ngx_pagepseed worked great for some time until I ran into issues with latest nginx versions. I’ve tried Cloudflare, but ran into issues where webp images are served to iPhones and those images were not displayed/rendered.

Im wondering if willnorris/imageproxy + CF + some kind of css/js based webp loader would address the needs, but then again it’s a lot of effort for something that might end up working out of the box in WordPress, so doing and undoing everything seems like a lot of work with little benefit.