Ashbeen thinking about how a web browser based more on plugins that interpret data rather than just an html renderer might work
ex. instead of the standard mastodon experience of going to mastodon.social or whatever and loading a bunch of html & css & js to render toots, the server would just send you raw toot data, which a browser plugin would convert into a renderable format (and if you didn't have a plugin for it, your browser could ask the server for a suggested plugin)
with that format, you'd avoid a lot of redundant network traffic from sending the same formatting data multiple times to the same browser, and it'd be easier for users to decide how they want their browser to show them data
of course, browser caches exist, too.
the best example of this that i've seen was Rotonde, which was a p2p social network using Dat. since your profile lived on your own computer, you could change the html & css & js as much as you wanted and it would still work (as long as you preserved networking with other people's rotonde instances)