Okay here is an idea for an RP.

Basically the players come from different polity's, whether Trek, Star Wars, UNSC etc only to find Atlantis under the ocean, submerged and no one can get into it. Suddenly it starts to rise. After that the players can then interfere in the events as they wish - and as this is AU, no characters are safe so should things go haywire; McKay, Carter, O'Neill could die.

Two factions that will likely be GM or Co-GM only are - Andromeda & Stargate.

Okay would there be interest in this?

Can you stop the Wraith acquiring the technology to take over the whole galaxy?

EDIT: Alternatively, this could always take place during Stargate Universe and you encounter their ship instead.

...Mmm. Fascinating. Crossovers are delicious. I'm in.

Would the Atlantis/Destiny crew from the original timeline still be there? Or would this be an entirely new spin on things?

For Atlantis - yes there would be some SGA crew there; for Destiny they don't really bring anything to the table to be honest.