You should give Home Assistant a go! It’s an open-source Home automation platform, managing all your smart home device from a single place. Being open source, it supports almost everything out there, and anything that is not supported out of the box is provided by the community.
I would say option 2 (proxy with cache), where you only download requested images and try to cache them for a reasonable period of time that allows most users to see the post on the front page without much problems, and delete it afterwards (I’m not sure what value this would translate to, I’ve seen mentions of 48hours but that might be either too much or too little, I guess you know best what would work). I mostly use Lenny to browse new content, so that is most important to me. If I would ever go and explore older posts, I won’t mind older images possibly being broken.