I like the plan, and the comment about Inverness rang bells with me. I tried that, and got a long way with it BUT plenty of people said what I am about to say to you, and in the end I agreed. Very nice, how many operators are there going to be, are there really going to be simultaneous movements? How is your wiring and electronics design, can you make slow and stop circuits so you can drive one set out and let the incoming set look after itself? Could you really use all that track?
I wonder about P1. It can only serve the anti-clockwise loop and despite its run round facilities (and I agree some variation of movements is entertaining) seems a little lost. Stock could be pulled out and propelled into P2/3 by a pilot, blocking the anti-clockwise circuit whilst you did that of course. BUT the more easily used upper part of the station feeds to this lower less usable part.
You will be dependent upon maintaining a balance between the two halves Drawing/propelling by a pilot will be a feature of this layout unless you are using a lot of EMUs/DMUs.
Can I suggest you should think about whether you want a dumb-bell. There is some good advice about not having curved fiddle yards. You could remove P1 and remove the dumb-bell and (if there is space of course) put a standard fiddle yard on the end of the first part of the curve making an L shape.