Thanks for the replies.
Regarding access areas - or lack thereof. The "access aisles" I have labeled are basically just places that I won't lay down any plywood/OSB at all.. all track in those areas will have to be elevated on trestles/bridges or inside a "mountain" and supported by wood risers. The main issue is with the staging yard at the very bottom of the layout. Let's assume that is somewhere else entirely for now...
With that layer turned off, you can see there are multiple areas that are contenders for access areas.
As you can see in the attached picture, the high-line track layer is fairly isolated over the aisle part of that middle area. It's also elevated in with the grey sections. It wouldn't be prototypical, nor easy, but If I make that whole area elevated on a trestle or bridge, there "valley" below it could be lifted out - or possibly left open.
As for the turntable area. That will have to be dead flat to work correctly anyway, so one thought was to put the turntable and all tracks on a pop out panel. If I shape it correctly, I can make it like a manhole cover that can come downward allowing me to stand in the middle. As you can see in the second picture, even with the staging yard and staging reverse loop layer turned on, there is quite a bit of space available. All the "hidden" track underneath will be on wood risers, so that can all be accessed from under the layout.
I will take all of these comments into consideration though, and I appreciate the pointers. One of the options I've considered is to put the staging yard in the "work room" from the original post (Room Overview). I think that will alleviate 99% of the access concerns (if access is done from underneath. However, that requires a hole in the wall and approval from the spousal unit.
I did this original track plan using MTH ScaleTrax (hence the other posts over my concern about the potential loss of it) so I have to redo it with Atlas or Gar-Graves. I'm leaning toward Atlas - but this will affect the curves and turnout placement quite a bit. MTH has #4 and #6 turnouts, fantastic flex track, and O-72 and O-80 curve sections, while Atlas has #5 and #7.5 turnouts, poor flex track (from what I've read) and O-72 and O-81 curves. However Atlas does have larger diameter curves that may reduce my need for flex track. That said, the nearest thing they have to match my flex 44" radius curves is O-90. I haven't done a thorough investigation of Gar-Graves - but I know if I go that route I'd also need to probably use Ross turnouts.
Decisions, decisions...
