If I am remembering correctly,
many of the central provinces are tagged with the "many sites" terrain flag and all of the farm land provinces are tagged as "large", so very good income unless scales destroy that.
If you look closer (in game it is obvious I think), the brown lines that you see are bridges which connect the outer spokes. In my current game, I have made a priority to capture these choke points and fortified them to protect my rump and now have a sizeable force making a run for the central ring.
Play wise, I am quite happy with the map so far. Time will tell. If the AI spends too much energy pounding each other and lets me have an easy victory point win, I may have to rethink it.
(Feel free to ramble. I do it all the time.
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