Fair; re-reading TFA, now I realize you explicitly instructed me to stop reading in the first paragraph :)
Trying to redeem myself with an on-topic question: isn't what you want more of a "refactoring of Blink" than "building a browser engine"? I would be surprised if a complete rewrite was really necessary for the features you want, since "saving state" already happens to some extent in all engines (even if it's just reloading from the cache) and I've seen reports about Gecko integrating multi-core cascade from Servo. What makes it hard to incrementally improve upon the current engines?
Indeed you can incrementally improve existing engines, and certainly that's what you would try to do if you wanted one of those specific features. But I didn't write the post because I want those features, I wrote it in the hope that it might be helpful to people who are already planning to write a competitive browser engine from scratch.
Yes, for almost every conceivable features you'd be much better off adding it to an existing engine. Maybe you won't get buy-in from the core maintainers, so you'll have to maintain an out-of-tree branch, but that's still going to be much less work than doing your own engine.
Trying to redeem myself with an on-topic question: isn't what you want more of a "refactoring of Blink" than "building a browser engine"? I would be surprised if a complete rewrite was really necessary for the features you want, since "saving state" already happens to some extent in all engines (even if it's just reloading from the cache) and I've seen reports about Gecko integrating multi-core cascade from Servo. What makes it hard to incrementally improve upon the current engines?