It's trivial but not safe in the sense that code that previously depended on some global state setup done in the master process right before fork will stop working. If this code is a library that is not in your control, you might not be able to "just revert" to fork mode easily.

And that change should be made for every platform so it will affect a much broader group of users than are affected by *this* issue.

Another thing is that some application packagers (at least Facebook's XAR but probably many others) don't work with "start" by default.

So don't take this lightly, just as Davin is saying. That being said, it's probably wise to change the default to "start" which is a better method. And if we *are* changing, doing it sooner rather than later makes the most sense.