So, I've been working on an Indiana based Pokemon Region and what I have so far is:

+The Map with Gym Cities, Starting Town, and Champion (Some are named)
+What Town Gym Cities, Starting Town, and Champion are based on.
+Some "Post-Game" Stuff
+Typing of each gym & the elite four (not ordered yet)
+How Town Names Are Linked (Town Names still somewhat resemble the name of the town their based on)
+What The Grass Starter is Based Off (Corn + Stegosaurus)

Typings are:
+First Gym~Flying
+Second Gym~Dark
+Third Gym~Ice
+Fourth Gym~Steel
+Fifth Gym~Fairy
+Sixth Gym~Ground
+Seventh Gym~Psychic
+Eighth Gym~Water (Mentioned to be Formerly Poison)
+Elite Four~Electric, Grass, Ghost, & Poison

All of the gym types (apart from Fairy) have something to do with the town their town is based on.

Also, yes, the Poison Type Elite Four member was previously the Eighth Gym Leader before getting offered the Elite Four position. This actually is what ends up causing the post game in said town to happen.