User blog comment:NejiHyuga2/Waifu Wars via a What-if Scenario/@comment-36273071-20190309111955

As BoC said, it's mostly just personal preference. Although, Kallen might face some serious prejudice for being a halfbreed, prejudice which wouldn't be easy to solve while remaining a good emperor. On top of that, she is known to have been a terrorist at first- whereas most newer recruits joined the Black Knights due to it being an official army, she began in a branch of those useless, molotov-hrowing, hostage-taking madmen.

Anya would actually have some solid basis- she seems to have been good friends with Lelouch and Nunnally in the past, before they were mind-wiped to forget her. She even seems to be friendly to him nine years later, when she becomes a student at Ashford. Plus, she is a Knight of the Round, so many might adore her.

Marriage between C.C. and Lelouch, despite my love of the ship, would be very hard to execute. At best, she is just a commoner, so some would see a Charles/Marianne situation from years ago. At worst, she is someone who does not even exist, and has no official documents except for coverup/espionage identities. And trying to explain just why she doesn't ever seem to age in comparison to her husband would be impossible.

And then there's the alternate options where he marries Suzaku or Nunnally. Which, ironically, probably wouldn't even cause any commotion- there seems to be no heteronormativity concept in Britannia, and the latter option wouldn't be that uncommon in a royal family.

...while I'm still here, have this.