Building off what Snyder and Goyer wrote, I think that this would the the best route they could take if WB would give DC more creative control over the movies. Wonder Woman deserves a good origin story based heavily on ancient Greek mythology with a cast of strong female characters. Flash doesn't need a long origin story, it could be told in a 5 minute flash back and since Barry Allen and Hal Jordan are good friends they could appear together in the same movie similar to Bruce and Clark. At this point you have the 5 core characters you'll need for a successful JLA. Batman and Superman movies make the most money, so each phase will start with a film for one of those two characters which will help finance the rest of the films. This is just an outline I put together before which I have updated. I know its far fetched but I think its possible.
01. Man of Steel (2013)
02. Worlds Finest (2016)
03. Amazon: Diana of Themyscira (2016)
04. The Brave and The Bold:
Flash & Green Lantern (2017)
05. Justice League of America (2017)
PHASE II:
01. Death and Return of Superman (2018)
02. Batman: Heart of Hush (2018)
03. Amazon: Eye of The Gorgon (2019)
04. Green Lantern Corps (2019)
05. Aquaman: King of Atlantis (2020)
06. The Brave and The Bold 2:
Green Arrow & Black Canary (2020)
07. The Flash (2021)
08. Justice League of America 2 (2021)
PHASE III:
01. Batman: Under The Red Hood (2022)
02. Teen Titans (2022)
03. Superman: Man of Tomorrow (2022)
04. Amazon: A League of One (2023)
05. Green Lantern: The Sinestro Corps War (2023)
06. The Flash 2 (2023)
07. Aquaman: Throne of Atlantis (2024)
08. The Brave and The Bold 3:
Black Lightning & Vixen (2024)
09. Billy Batson & The Curse of SHAZAM! (2024)
10. Hawkworld (2025)
11. Batman: Return of The Demon (2025)
12. Justice League of America 3 (2025)
PHASE IV:
01. Green Lantern Corps: Blackest Night (2026)
02. Batman & Robin Reborn (2026)
03. Superman: New Krypton (2026)
04. Aquaman: Death of a King (2027)
05. The Flash 3 (2027)
06. Green Arrow (2027)
07. Amazon: God of War (2028)
08. Billy Batson & The Curse of SHAZAM! 2 (2028)
09. Justice Society of America (2028)
10. Batman: Night of The Owls (2029)
11. Cyborg & The Metal Men (2029)
12. Justice League of America 4 (2029)
PHASE V:
01. Batman: Death of the Family (2030)
02. Green Lantern Corps: Wrath of The First Lantern (2030)
03. Green Arrow 3 (2030)
04. The Brave and The Bold 4:
The Atom & Booster Gold (2031)
05. Legion of Superheroes (2031)
06. Stormwatch (2031)
07. Firestorm the Nuclear Men (2032)
08. Doom Patrol (2032)
09. Young Justice (2032)
10. Zatanna (2033)
11. Doctor Fate (2033)
12. Justice League of America 5 (2033)