Here's another random idea, fusing Gundam SEED and Gundam 00 into one timeline.
The world setting is more or less that of 00 Earth, with the Union, AEU, and HRL replacing the world powers in SEED. Australia's under ZAFT control while both Africa and the Middle East are a mess. The Plants were originally created to assist in constructing the upper sections of the orbital elevators, eventually declaring their independence from the three power blocks and moving to form Plant as it's seen in SEED. This would likely heat up tensions in advance of the Valentine War, and make the actions of one terrorist group spark off the powderkeg. Yes, this means that Blue Cosmos is nowhere nearly as supported by the governments and militaries of Earth as it was in SEED; it's more or less a privately funded terrorist organization meant to promote warfare for the sake of arms manufacturers.
Anyhow, that's just some background for the start of events in 00 Season 1 and SEED. It starts out at the Micronesian islands of Orb space colony Heliopolis, where the Union is working with Orb engineering teams to develop new midweight mobile suits (the G-Weapons) with advanced technologies to better compete against Zaft's GINNs than the current Realdo and Flag models. Orb is more or less forced to help due to the Union's assistance in financing the construction of Heliopolis, and Zaft's take-over of Australia, which is disturbingly close to the HRL's orbital elevator and the Orb home islands. Cue up the events of SEED, with Archangel first running to the AEU space fortress of Artemis for protection, and then arriving in South Africa upon re-entry and getting involved in all kinds of messes.
In the background, Celestial Being is starting its actions. The two storylines will begin to merge in the desert battle where all three power blocks work together to take down the Gundams. Mu's considered an ace by the Union, of course, so he's temporarially reassigned to the Overflag squadron for the mission. There might be an armed intervention by Celestial Being beforehand, though, to destroy the 'false' Gundams.
In an amazing twist of events, the Archangel doesn't desert the Union after the battle of JOSH-A. Everyone present is surprised by a Blue Cosmos attack and scatter to the four winds. Archangel leads a small fleet to Orb where they're ordered to prepare for an invasion of Australia or possible attacks against the HRL orbital elevator by Zaft. Meanwhile, Flay's off with Rau, Natarle's been given the Dominion and ordered to defend the Union's orbital elevator, and Mwu's been given a GN-X and assigned to anti-Gundam operations. Yeah, that means Cagalli got lucky and is now piloting the Strike.
Due to the orbital elevators, the mass drivers of the world aren't nearly as important strategic assets as they are in canon SEED. So when Zaft takes on and destroys the Union driver in Panama, there's no rush to take over Orb's. The war shifts into space and things start to wind down. Celestial Being's on the run from the UN forces due to the arrival of the Tau drives, Blue Cosmos now has the specs for the NJ Canceller and is fitting nukes to be used again, and Zaft's being pushed back to the Plants. Blue Cosmos tries to launch nukes and destroy the Plants, causing both Celestial Being and the UN forces to temporarially put off their dispute and assist in defending against the illegal use of nukes. The Valentine War ends in a cease fire, and the UN chases Ptolomy to Lagrange 1 to finish destroying Celestial Being.
End Season 1 and SEED.
Then comes S2 and Destiny...
I haven't given the second half much thought yet, but it's definately going to follow Celestial Being's actions much more closely than the first. Mostly, I'm concerned that this is going to end up being a twenty Xanatos pileup with every hidden group's master agenda being played out against one another.
What I do have in mind is the Federation unifying much of the Earth as in canon 00, only leaving Australia to Plant. Southern Africa and the Middle East are the current hotspots of activity, and the A-Laws are quite busy there. Blue Cosmos has rebuilt itself in the last four years (Daggers, Windams, and canon SEED warships in small numbers) and has staged another attack on the Plants. Officially, the Federation condems the attack despite privately hoping to obtain the remote charging system Zaft has developed for rapid recharging of its Tau drives. Zaft is EXTREMELY glad that the A-Laws are focused on combating 'terrorists' on Earth, especially after a Momento Mori shot vaporizes Junius Seven's fragments before they re-enter the atmosphere. Gilbert wants to unite the world against Blue Cosmos/Logos under his Destiny Plan, Logos unleashes its Destroys, and Ribbons is enjoying the sideshow from his big couch.
I don't know, the more I look at this idea the bigger it gets. Maybe it needs to be simplified a bit. Ideas, questions, comments?