Here is the thread where some people were using browsers in QEMU: AQEMU-QEMU: Virtualizing on Haiku as host
The general view there seems to be it was slow.
On that note hardware accelerated virtualization has been mentioned quite a bit in these forums and would greatly increase the speed of virtual machines, including for this purpose. This would be good for all kinds of things and I expect at some point someone will do the work.
As for this idea, as everyone says WebPositive needs to be made as good as we can make it, and I think it should be possible to make it as nice as Safari, which is pretty decent. The only thing technically we cannot do right now is GPU accelerated drawing, which is probably mainly for some aspects of compositing the rendered web page, some canvas stuff, videos and WebGL. Everyone seems obsessed with GPU acceleration, but this blog post from 2014 shows that GPU acceleration is not really a slam dunk in improving things. A lot of things in computing are like this.
So if people think Haiku can never have a great browser as long as we don’t have GPU drivers, that probably is not true. I say this because I was kind of in the GPU camp myself but now I’m not so sure. For games obviously the GPU is critical, but no one is porting <insert big 3D game here> to Haiku anytime soon. Long term obviously we want the GPU situation fixed but my main point is it is not a roadblock to a good browser.
Unfortunately a lot of web developers only build for and test on Chrome, which is kind of a problem if your only browser uses WebKit. The best solution for that now would be to use Chrome in a virtual machine. There is almost zero chance Google would ever port Chrome to Haiku, and from what I have seen they are even kind of hostile to take patches from outside to port Chrome to a new platform. But maybe the Blink rendering engine could be ported and used in a new browser kind of like Microsoft did with Edge. But we certainly are not Microsoft and Blink already works on Windows, so I don’t know. It would also probably be a huge amount of work. At this point browsers are more complicated than operating systems, well certainly one like Haiku.
To summarize our best hope is to continue making WebPositive and our WebKit port better, then hardware accelerated virtualization would making running browsers in virtual machines faster.