Dear Matt:
Please forgive me, but you are going to be aggravated with your self. Your layout is way too deep. It will be heck to have to reach back there by the wall to build it, clean it, work on it, etc. Don't do it to yourself! Trust me. This is by far the most common mistake O scalers make. Watch this video please:
https://www.youtube.com/watch?v=2ebtbblFkeA
I'm not trying to make you aggravated or upset with me for butting in. I'm trying to share great advice, experience and wisdom with you and in the process save your knees, back and the desire to kill yourself once you realize the money you spent making this far too common layout design mistake. If you proceed and build a layout that wide, you will remember that I wrote this to you.
I had a "bonus" room exactly like you in the photo not long ago. You have a fantastic chance and great space to construct a layout that will be good. I write this with the greatest respect to you in my attempt to spare you money and aggravation...don't do that to yourself! I can't begin to tell you the number of people that have.
If you want to send me the entire measurements of your entire room/area and what kind of railroad you want: toy, display, operational, combination? And if known: what is the name of your railroad or what railroad do you like--your favorite? What will be the railroads purpose? Entertain kids? Sit and watch? Is it for freight? Passengers? Both? Other? I would respectfully suggest: Make it operational so that you, your wife and others would play an active role in the setup to maximize your enjoyment.
Also, I'm guessing that you are more interested in a main line than switching based upon the drawing??? Is that right?
The most critical thing to know/learn is this and I've been doing this for forty-five years. I don't know everything, but I can tell you this: no one can reach across 48 inches or more. If they could, they'd be on a NBA team.
Lastly, if you go forward with that plan against the wall, at a minimum, figure out how you will reach everything--within 30 inches--meaning cut access holes, put it on wheels, etc. to move it away from the wall.
Peace to you.
RESPECTFULLY,
John