First of all, I like the concept of your plan which looks like it will be a lot of fun!
I like Tim's revision giving you a passing siding on the mainline. It also eliminates the back to back switches making a tight 's' curve which would likely be a source of derailments. Also, you could run 3 trains with his version - one inside switching/running, two outside alternating turns on the mainline. And of course switching from inner loop to outer loop.
Another side comment on design, is that some people prefer when they can reverse direction of the train going clockwise to counterclockwise and back to clockwise. Currently, you can only change from counterclockwise to clockwise. Once you're going clockwise you can't switch back without picking the engine up with your hand. Not a huge deal, but might be to some and should be considered.
As far as powering the track and accessories (I assume you are running conventionally), personally I would separate the power into 5 categories:
1. Track: Outside mainline (includes blocks for the passing siding)
2. Track: Everything else inside
4. Accessories (low power)
5. Accessories (high power) some accessories like more juice to optimize performance
Just remember, that the power districts should all have the same common. And if more than one transformer is used, they need to be phased.
Which transformer(s)/power supply do you plan to use? This will lead to greater detail in how to complete the wiring.
To separate power districts and blocks, you just need to insert a fiber pin into the center rail where it touches another block. For example, at the top of the plan, where the mainline switches to the inner track, you would place the fiber pin between the two switches.
Two primary questions for you:
are you operating conventionally or using tmcc/legacy/dcs or Lionchief ?
what is your power supply?
all the best,