Pretty much down with that theory except:
If Rick Origin Memory is real, I think 'our' Rick is more likely the one that was working for early-stages Citadel recruiting other Ricks. Rick's relationship with the Citadel makes the most sense if he was a major part of it in the past, and based on combo Rick memories in Close-Rickcounters and photos at Birdman's house we know that Our Rick was around Morty as a baby. It's possible that's another Rick / timeline / whatever, but that would be a lot of red herrings.
And totally unfounded personal theory on President Morty:
I think he's the abandoned credits Morty, but isn't trying to kill all Ricks, he's trying to prove a point to 'our' Rick, The Rickest Rick that he has ascended Mortydom and become master of Mortys and Ricks. He's not trying to kill his Rick, he never meant to target him during the original plan. Since C-137 Beth hadn't seen her Rick since before Morty was born, and we don't even know what they jumped to after Rick Potion #9 that Morty's semi-automated system for eliminating Ricks to get Mortys probably had no idea he was picking up his original Rick, and had no intention to ever try and kill him there.
And non-episode spoiler stuff:
A character makes an off-hand but direct-to-camera, center-of-focus hy-phen-ated remark about citadels in the multiverse. What's up with that? I thought the whole point was that the citadel was a fixed point in the multiverse, not in space.