It does not take the same order of engineers for only integration. That is false as you can see by the existing integration teams for forks that exist. And I'm sure Mozilla is able to find talent capable of working on web engines.
There are no Blink forks with appreciably large differences yet, though. In the aftermath of Google turning “evil” and working against the better interests of the web in multiple ways, you’re looking at a fork with divergences as large or larger than those that prompted Google to fork Blink from WebKit, making integration of patches from mainline Blink a full time non-trivial job.
Personally I’d rather see Mozilla working on Gecko or maybe consider switching to Servo or something instead.
