I like the plan. But are you sure you want a single track main? Your layout is big, but not that big- on almost every circuit one train would have to stop and wait in a siding, especially if the trains are running in opposite directions. Would there ever be a time when you and a buddy would just want to run two trains continuously with no chance of collision?
Given your space and ample yard capacity, I would also be tempted to add one more industry, maybe somewhere on the right side of the plan.
I like Lionel's Legacy system. It's the evolved second-generation of TMCC. It's robust and not picky about how your layout is wired. Cross-grading other manufacturers' locos is possible with aftermarket boards from Electric Railroad (ERR) sold by 3rd Rail. If all of your locos are Legacy / TMCC, you don't really need any blocks. Just a big stout power supply, and 18 volts on the rails everywhere on the layout.
When you build it, I hope you invite me over to run trains with you! :-)
