The thing is, if you can make it run the top 10 websites (google, facebook, youtube et all) and convince the maintainers of those websites to always test on thi

The thing is, if you can make it run the top 10 websites (google, facebook, youtube et all) and convince the maintainers of those websites to always test on this thing before each release that would already bring a giant win for most users in the planet, and websites that have features outside the scope of this thing would fallback to standard rendering; in such world (and if it gains momentum) developers would slowly move to avoid features that this doesn't support in order to get the performance benefits it brings.