Vyzzuvazzadth
Yazzavedth Zayann
I agree with Fez and want to add to that.
The only way I can see an Aerith DLC being done without screwing with the story and canon would be showing her journey from the Temple of the Ancients to the Forgotten Capital, her fate and then her second journey through the Lifestream from understanding her situation over acquiring the skill to retain her spirit and personality, traveling the Lifestream and finally saving the planet with the Lifestream's help, possibly even controlling it directly after Sephiroth's influence has faded away. Kind of a "Another Side, Another Story" situation.
The only way I can see an Aerith DLC being done without screwing with the story and canon would be showing her journey from the Temple of the Ancients to the Forgotten Capital, her fate and then her second journey through the Lifestream from understanding her situation over acquiring the skill to retain her spirit and personality, traveling the Lifestream and finally saving the planet with the Lifestream's help, possibly even controlling it directly after Sephiroth's influence has faded away. Kind of a "Another Side, Another Story" situation.