I won't go by year by year, but, I'll go area by area. I'm afraid I'm going to show my Otaku side here.
International Street: Ad a zipline that goes from the first deck of the Eiffel Tower to the old International Restaurant. Turn tower gardens into a Kings Island History exhibit like what they did for KI 20th anniversary where Skylab used to be.
Coney Mall: Put in three flat rides where flat rides used to be but were not replaced. Skylab, Flying Eagles, Flight Commander. I'd say a Gerstlaur Sky Roller, Zamperla Wave Blaster, Chance Free Style. Return the backwards Racer, and motion seats in the FX Theater. Make an original 3D Motion film based on Phantom Theater.
Rivertown: Return the scenery and animations to the train. There is a great wooded area over by The Beast behind the old Crypt building. This would be great for another river type ride. I'd say a Bayou themed Splash Battle. Get rid of the Crypt building and build an S & S Free Fly X
Oktoberfest: I'm not sure what to do here since there is not much in the way of room. Perhaps maybe a giant wheel, or an ABC Rides Giant Smart Swing http://www.abc-engineering.ch/cms/front_content.php?idart=100
Planet Snoopy: Give the Peanuts the boot and get a cartoon company that has current programming. Since Hanna-Barbera no longer exists but in name only and Six Flags doesn't seem to want to do anything with the product, Time-Warner is a free agent anyway since they no longer own Six Flags, I'd go with Cartoon Network. It brings back some of the old Hanna-Barbera Characters as well as current CN characters. I'd gut out Boo Blasters and the old Enchanted Theater and put in an Adventure Time dark ride where you battle Pepper's Ghost monsters, The Ice King and Marceline. An SB International Flintstones Themed Car Ride. A Kid's Next Door Themed Heege Tower Ride. Zierer Jet Skis. I kind of went Legoland on this, but, I kind of wanted a kid's area that wasn't a copycat area of Six Flags or every other family owned park.
Action Zone: Once Paramount left Action Zone just became another Coney Mall with no real theme. I fact the only ride themed after the movie it was named after was Top Gun. Face//Off and Drop Zone had a movie name, but, no real theme. I wanted to make a theme area based on Sega's Joypolis http://tokyo-joypolis.com/ and J-World Tokyo http://www.namco.co.jp/tp/j-world/. Shonen Jump's Action Zone featuring anime and manga shows and characters from Viz medias Shonen Jump magazine. Amazon Falls will be remodeled and extended covered and themed to One Piece. Banshee will remained the same. It's the only ride in the area without a stupid name. Drop Tower will be renamed and themed to Fullmetal Alchemist, Fullmetal Freefall, and so on. Interactive games, and shows.
One questions. How often is Timber Wolf used? It doesn't seem like it is used at all.