I dived Okinawa when I was stationed with there with the Marines in 1981. Made lots of dives but don't remember all the neat stuff you've mentioned. I remember really neat wall dives and lots of sea snakes !!!!
I agree many Military Divers Dive the seawalls every weekend. There is nothing wrong with that as it is convient, easy, and cheap. I also spend a lot of time diving the seawalls but usually in the form as a divemaster supporting and instructor. When I dive for fun I love to get off the beaten path. I will do a boat dive, or drive to the far side of the island and try to find a new dive site. I use many publications both US and Japanese to find these dive sites. We dive for the adventure. Half the fun of shore diving is the adventure getting to the dive site. The dive shop I work for offers Dive and Drive where I can take you to these little known dive sites. My future plans include loading a bunch of tanks into my van and putting my van on the ferry and going to the outer islands for a weekend. If will cost me about $100 for the ferry ride. We will camp out on the white sand beach and be able to dive very remote locations.
Onna Village has some great wall dives. I like to do a shore drift dive. Using known current direction we enter at one point and drift in the current along the wall and exit out at a second point. We ground our gear on shore and I walk up and pick up the car and move to the second point to pick our gear.
We do have sea snakes and they will get any new divers heart pumping! Sea Snakes are pretty harmless especially if you are wearing a full wet suit. Last weekend I dove off the seawall with a large school of Baracuda (1000's) circling around with in a few feet of me, and that was a real National Geographic Momement right off the sea wall.