So I’m just thinking about how this would work, in a perfectly non-competitive world:

There’d need to be some Browser Standards Association to implement and suggest browsers to add to a list of “certified browsers”, with transparent requirements to be included to ensure low quality or outdated browsers aren’t included. The OS would need to implement that entire list in a randomized format. There’d preferably be some sort of built-in pros/cons list of the browser, I suppose these could be put together by a combination of the BSA and the competing browsers.
But these pros/cons won’t be understandable or significant to 95% of people.

The BSA would also want to ensure there’s diversity not just in browser and companies (like Opera getting 3 fucking entries), but would also want to ensure there’s a variety of browser engines (preferably not just chromium and webkit).

Complex? You install Firefox and two seconds later it’s pestering the shit out of you to make it the default browser