I wouldn't do to much to the Flash mythology to drastically change it, however there are a few things I'd alter about Wally West and the rest of the supporting cast.
For years, we've seen Wally as DC's Flash after Barry's death and then we received 2 Flashes. Barry returned from the dead and became the Flash once more of Central City, while Wally remained the Flash of Central City's neighbor, Keystone City.
While having two Flashes around, both in neighboring cities is a good idea, it is a bit confusing. Barry Allen and Wally West's costumes are similar but to the avid fan, a difference can be seen. Barry's symbol is a double dash lightning bolt while Wally's is a single dash lightning bolt that resembles an "S" for starters. Barry's lightning belt wraps completely around his waste while Wally's separates at his torso. Since Wally's symbol resembles an "S" in appearance, I would change his name to "Surge" and make Impulse his sidekick while new Kid Flash would be Barry's sidekick.
Jay Garrick would remain the Original Flash but having retired from crime fighting he acts as a mentor to Barry and Wally. The Flash Museum, since dedicated to all of the Scarlet Speedsters, would be located directly on the border of Central and Keystone Cities, with Jay Garrick as the curator. I would return Wally to being not wealthy but well off after winning a lottery. Iron Heights Penitentiary would also be located on the line that separates Keystone from Central City. Wally will act as a member of the parole board for Iron Heights.
Now let's take a look at the world of Green Arrow. I would maintain most of his origin and history as well as his marriage to Black Canary. I would however change Conner. I think it's important for Ollie to have known about his son and having built a secret relationship with him from birth and training him. Conner Hawk would join his father in Star City and become known as Black Arrow. Conner chooses this name to honor both his father, Green Arrow and his step mother Black Canary. It would be revealed that Roy Harper was the original Speedy but shortly after Ollie fired him, he was kidnapped and cloned. Roy would discover his clone who shares his memories and skills while in the laboratory and the two would escape together only with the real Roy missing an arm do to it having been surgically removed for the cloning process. Oliver discovers what happened to his former ward and takes both him and his clone in, and builds a new arm for the real Roy Harper. The clone takes the name Red Arrow while the original takes the name Arsenal. Also included into this rebooted timeline are a new Speedy, Arrowette and Artemis. Arrowette and Artemis are sisters and the nieces of Oliver.
About The Author:
I have a huge collection of both movies and comics... As a kid and teenager I collected Marvel but within the past few years I've mainly gotten into DC Comics particularly Superman, Batman, Green Lantern and Firestorm. Other favorites of mine are Outburst and The Ray. I've recently started getting back into Star Trek which TNG was one of my favorite shows as a kid. I'm married to a beautiful woman named Elizabeth have 2 girls (Marissa 9 and Alexandria 2) and a son who's a year old named Edward. I own my own handyman and lawn care business. I can be reached outside of comicbookmovie.com @ http://www.facebook.com/LanternStorm1369