Okay, I need to stop. I believe I asked earlier, but never saw an answer or I may have missed it, but since you seem to want to expand on this design I need to know what track you plan to use.
You've mentioned O54 curves in the past, but just now you mentioned using O48 curves for the North Pole loop. That suggests you plan on using FasTrack since I believe it's the only brand that has O48 curves. If that's the case, it makes a big difference to the design software I use.
If you are going to use FasTrack, the outer main will have to be changed to O60 if you want to run anything that requires O54 or wider curves. The same applies to the reversing loops. All the switches will have to be changed and that will affect the loops and storage yard. It's not a big deal, but I'm not going to spend any more time changing things until I know what track library to use.
