You can already get from Newark Penn to the airport using NJ Transit. It isn't a terrible idea to bring the PATH there so there's a single seat ride from places that PATH services but NJ transit doesn't, but that doesn't apply to Newark.

Yes, I wait to transfer and pay again.

The PATH is cheaper, runs more frequently, makes several more stops in Manhattan and NJ, so it would be a better option.

If you want to go downtown, for example, the PATH goes to WTC, as well as midtown.