This seems like the kind of thing CDNs should be offering to do for you, or at the very least have available in their app marketplaces. The idea isn't even that

This seems like the kind of thing CDNs should be offering to do for you, or at the very least have available in their app marketplaces. The idea isn't even that complicated. But I love the MITM model here. Get file from origin or cache, parse, manipulate, pass on. Pretty cool.