Here's something I put together this evening. This table utilizes a 6" extension to make the table 78" wide to hold the O-72 track. I used Lionel track and the switches and straight sections in your image and added some half straights (#5505), O-72 swtiches (#5165 & #5166), and a couple of long straights (#5523). I preserved the figure-8 for turn-around and altered the inner loop to incorporate a small yard. I'm not sure there's much room for buildings, though. I doubt you'll use switches at all 4 corners of the O-72 loop, I was just putting ideas out there for how the corners could be used. For some reason I can't remember how to post the actual SCARM images tonight, so I've got the "3D" image, plus the SCARM file. For your convenience (or inconvenience, perhaps), I've used my inane color-coding system to designate certain areas of the track in the SCARM file for different purposes: blue = main line, cyan = alt. main line, red = turn-around, yellow = yard, purple = industrial/commercial.
Advantages of this design is you can run 3 trains simultaneously & not get in each other's way: one on outer mainline, another on figure-8, and another switching in the yard. If desired you could flip the switches on the inner 2 yard tracks to more frequently free up the entire inner loop while still doing some switching. However, at times you will still need part of that loop for a run-around.
Disadvantages would be a lack of room for actual buildings to go to & from, as well as general scenery. However, IIRC you'd said at this point in time that wasn't a priority for you. If you change your mind, you can always widen your table a bit. Everyone here wishes we just had another 2 feet....
Anyway, hopefully you like it; let me know if you have other thoughts, etc.
