It’s a great start to solving a new problem. It’s not a perfect solution, but it doesn’t claim to be. What I like about this solution though, is the impact on the designer is negligible. Also, the tech already exists, so there’s no major hurdles once the issues get addressed.

Thanks for your effort, Matt.

A possible improvement is to use Cron to check for images of your required sizes and generate them if need be. this way you dont have the security issue of the web server user generating images. Also this should be more compatible with a cdn. How often you want cron to run depends on how busy your site is and how often the images change.