Warning: Very Long
Ok, first of all I would add a new area behind Racer and by FOF, kind of like what StXBomber said. FOF would return to its original glory and I would make a new movie so that you don't see it 5 times over again when waiting in line. The military costumes would return too. I'd also rip out the helicoptor tours and I would put in a 4D Coaster. The coaster would feature the wickedest elements ever found on a coaster, it would be even better than X. I would make sure that the coaster doesn't have any down time. I'd also probably add either a Jump2 or a Topple Tower.
Next I would tear out TG and add a B&M Invert called Top Gun. It would be a cross of Montu and TG:TJC. The ride would feature a batwing that would go through a mist-filled tunnel under the SOB's que line. It would be just like the one at PC. The coaster would also feature an immelan that would come very close to SOB's structure. When walking to the coaster you will hear the awesome soundtrack of Top Gun. You 've got to love that music. Then I would tear out Congo Falls. In its place I would add either a Jump2 or a Topple Tower(Whichever one I don't put by FOF). I would also retrofit the bottom of Drop Zone so it could accomodate a ring of 50 seats instead of just 40. This would increase the speed and the capacity of the ride. The final addition for AZ would be retracking SOB with Intamin's Plug and Play track. This would offer a very smooth ride. The coaster would also get brand new trains and restraints that offer lots of leg room and a comfortable ride.
In Octoberfest I would take out Adventure Express and move it to another part of the park (More on this later) to allow for the tallest and fastest rollercoaster in the world. It would be an S-S Thrust Air coaster like H:XLC and Dodonpa. The riders would be launched from 0 to 150 mph in only 2.2 seconds and then sent straight up 400+ feet then come all the way back down 90 degrees. There would also be twists like on Xcelerator. The trains would seat 12 riders. There would be a new loading sequence allowing for more trains on the track which would increase capacity since S-S coasters suck in that category. Viking fury would be turned into a shrimp boat, too.
In Coney Mall I would take out all of the trim brakes on The Racer and add that last bunny hop that used to exist. What wonderful airtime would be experineced on this ride. Dodgems would receive brand new bumper cars since the ones now go so slow. All of Coney Mall would receive brand new paint jobs and would receive a facelift. I would hire Fyrfyter for the job because his ideas were kick ass. The action F/X Theater would stop showing SBSP3D and would show a movie based on 2 Fast 2 Furious. You would be the new guy racing and you would win. Ludacris would also be in the movie because he is awesome. In the line to get on the ride there would be tricked out cars like when they had DOT, except these wouldn't be Nascars. These cars would be awesome at night too. Vortex would stay but sections of the track would be replaced to offer a smoother ride. There would be no more headbanging and the ride would be awesome.
In Rivertown the country music will stop being played, wow can that music get any worse. I would also take out the trims on Beast's first drop and lessen the trims on the brake run to how they used to be. The Beast would be kickin ass again. The station would be a party again with the most enthusiastic ops. They would also get paided twice as much for working so hard. All the mantinence lights would be turned out every night. The land between the Antique cars and the International Showplace and the lake would be used for a new floorless coaster built by B&M. The coaster wouldn't be themed it would only be a great ride. This coaster would help bring some of the crowd from AZ to Rivertown. Also the other side of Antique Cars would reopen. A new area called Jungle Village or something like that would expand from TR:TR to the back of Nick Central. The area would include a new B&M stand up and would be named after King Cobra. AE would be moved to this part of the park and be rethemed to Indiana Jones. The tunnels would stay the same but the outside would be themed like Indiana Jones and the Temple of Peril. The ride would have the same awesome effects it used to have when it was first built including fog and lighting effects. A Delirium from Huss would be built too. A river ride like Jurassic River Adventure at IOA would be built. The drop would be bigger and steeper than Congo Falls an there would also be a bridge so people can get soaked. White Water Canyon would be revambed and rethemed. Also a new theater would be built and the theater would host a new Tomb Raider live action show that is somewhat like the Indiana Jones show at Disneyworld but only better. Wings Diner would be converted into a Tomb Raider restaurant with exotic foods. The restaurant would be themed just as great as TR:TR.
More additions would be put into NC and HBL to please the kiddies. Also there would be a new waterpark expansion and retheming of the park. Also a rollersoaker built by Vekoma would be built in the waterpark. The waterpark would also receive a new waterslide like Zinga at Holiday World with that awesome funnel. Plus more waterslides would be added and the waterpark would be much improved.
International Street would become more international and return to its former glory. I would hire Italianchef to revamp International Street and he would become the executive chef at the park. More events would take place during the day like they used to do. Bringing back the air show would be awesome and the parachuters landing on International Street would be cool too. It would remind me of the boat show at Universal Studios Orlando. Also the fireworks show at the end of the day would be spectacular. There would be a lot more fireworks set off and the show would be longer. The fireworks show now is just lame. I would also add a laser light show that would be awesome to see. The fountains would receive new lights to look as beuatiful as it did in the good old days. International Street would look awesome at night.
The shows at the park would be better too. There would be more action shows than just romance shows everywhere. I would end the young country show and add a more hip music show. The shows would get more attention and would be a lot better than they are now. Again they would return to the glory days.
Lastly I would build a Giga coaster built by Intamin. It would be taller, faster, and longer than SD200, breaking those records. The ride would be designed by the great Werner Stengel and would feature a Stengel Dive, overbanked turns, loads of airtime, and a fast paced ride. The ridewouldn't be built for the records but it wold be built for being the best coaster in the world. I don't know where I would put this ride but I would have to build it.
The park would feature something for everyone. I know this isn't pratical because it would cost loads of money but I think it would be awesome. I still have more ideas but I don't have enough time to write them and I'm sure you wouldn't want to read it either. Thanks for reading and lasting through this long post and have a great day!