Hmm, not sure it's for me (a bit too much hacker) but I'd definitely like a highly customizable, module based browser with a pure shell by default. Something like Visual Studio Code but with less cruft from the get go. I've never thought about it until I saw this! Now I'm really irked about there not being a solid, mature browser based on extensibility. Where the base is basically an address bar and history awareness…
Today I'm more interestea in turning the web into a more textual format to integrate it in acme (http://acme.cat-v.org/) which is already built around modularity. Making the web a content provider and letting me interact withit the way I want