Just a curious question here guys, I know using the re-linking process you can use another 300 series controller, say like a from P4 (GL300C) and use it as a replacement with a P3P (GL300A/B/C) but could I use the controller from a P4P+ (GL300F that's the one with the built-in monitor) on a regular P4? or even on a P3P?

As far as I know, not a chance.  

The P4P+ controller is GL300E.
You can set it up for P4, P4P and P4A no P3's

Agree with KedDK. You can control the P4 aircraft by choosing the right Remote Controller Type. And it is not available to connect P3P for this moment.