Maybe I am missing something, but I only see two reversing sections, the reverse loop on the left end of the layout and the point of reverse polarity where the two turnouts forming a crossover meet running from southwest to northeast.
I would use two auto-reversers, one to control the reverse loop and one to control the other reversing section. The question is, where to place the gaps on that reversing section to completely isolate it from the rest of the layout. That reversing section should be long enough to hold your longest train.
If it were me, I would select the passing siding directly above that crossover as the reversing section, assuming that it is long enough to hold your longest train. I would gap the crossover where the two turnouts meet, and I would gap the divergent end of each turnout that forms the passing siding. Those gaps would completely isolate the reversing section and, visually, it is easy to spot the reversing section.
Rich
Alton Junction
If you put the gaps where I show them, you can make the center section the reversing section and you only need one auto reverser. If you are afraid of two trains crossing a gap at the same time, use two auto reversers - one on each end. To be 100% sure of no problems, you would need one on each track of the right end (3 total).
So you can do it with one, two oe three depending on the amount of risk you want to take.
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A friend is building an N scale DCC layout to be controlled with an NCE PowerCab. The layout schematic can be seen at the link below.
http://farm1.staticflickr.com/335/31064943123_108eacb038_b.jpg
There are three reverse loops: one to the left (highlighted in pink) and two to the right, one inside the other (outer highlighted in green, inner in orange). How many auto reversers are required? The red dots are where the double insulated rail gaps are planned segmenting the layout into three power districts. Are these locations appropriate to the layout?
Any other wiring suggestions will be appreciated.