You could compress the hell out of the traditional jpeg codec/layer part of the image. It’d be there for backwards compatibility. It only has to be readable by older clients and “acceptable” quality.

See “49kb” example here — totally acceptable image quality for backwards compatibility.

https://res.cloudinary.com/thewebmaster/image/upload/c_scale,f_auto,q_auto,w_1250/images/blog/jpeg-images-definitive-guide/JPEG_Quality_vs_Size.png