I'm not sure that that's realistic. A browser in 2025 is arguably more complicated than an operating system, and requires fairly large and expensive teams of engineers to maintain and grow.

Google has billions and billions of dollars to throw at Chromium; I doubt Brave has anywhere near that kind of money. The longer it stays fully forked from core Chromium, the harder it's going to be to pull in updates, and the more expensive it will be to maintain.

I really am curious if that will hold up once bigger refactorings make the necessary internal APIs for ManifestV2 unavailable. Then Brave needs to maintain those APIs themselves, and every time downporting changes from the open source base becomes harder and thus more expensive in time and money.

I agree fully. We need to keep the idea of fully branching off from an open source project alive. But I also suspect that Google has incentives to make it extra complicated and difficult to maintain a fork of their codebase with adblocking implemented on top of it, over time. Resources are often very limited in open source and often comes down to one or a few people.