Earlier quoted context omitted.
Firefox already does that, started long ago. They even added support for -webkit prefixes for the same reasons.
As I can tell you from experience, they don't work all of the time, and it is a source of frustration for front-end developers I know who need to work with it.
Most of them have equivalent standardized features, or are in a state where you really shouldn't be using them. Don't expect every webkit prefix to work in Firefox.