I like the sentiment of this idea, but sadly I think that this will be doomed to failure. It is unfortunate (but understandable) that the browser plugin is required even to read messages or posts by people using Privly. Crypto solutions need to be dead simple to be widely adopted. If users have to download extra software on top of what they already expect, then people like my parents will probably not use this.
I'm not sure what the adoption or usage rates are for it, but a very popular Pinterest has its bookmarklet. This implementation couldn't be far removed from that.