Lex Luthor has already been told about the Zelig stone by Asabi. While Superman is caught in the Kryptonite cage, Luthor tries to gain Superman's powers, not realizing that it would switch their bodies and thinking it's a way to gain Superman's powers and still be himself. After using the stone on Superman, both men pass out -- Lex outside the cage, Superman inside it.

Awaking to find himself out of the cage, Clark (in Lex Luthor's body) runs out of the wine cellar, only to be taken directly to the top of the aisle (by a wedding planner) to await Lois, his bride-to-be. He doesn't yet realize that he's in Lex Luthor's body and he believes this is a Kryptonite induced fantasy that he gets swept away in to escape the pain of the cage.

By seeing Clark's kind soul and the over-abundance of love shining in Luthor's eyes when she reaches the alter, Lois quashes her doubts and agrees to marry him. For a split second, caught up moment, Clark (as Lex) says "I do" and becomes married to Lois as Lex. (The wedding doesn't get interrupted by the police, Perry, and Jimmy.)

After the ceremony, Clark needs to convince Lois of Luthor's villainy, that he's not really Luthor, and find proof the Luthor is a huge crime Boss, all in time to save his own body from dying in or escaping from the Kryptonite cage.

Ooooh! If I didn't have so many projects already... I hope someone takes this up, because this is a good one!

This is wonderful. In Smallville, Lionel switched bodies with Clark. And got a little too worked up when Martha hugged him.

I had forgotten about that. I really need to finish S9 and S10 of that show.

This is such a great idea!! (Not gonna take it, but somebody has to!) Which would he have to convince Lois of first? What would Lex do to find himself in the K-cage? And if he escaped?

Too many ideas. This has the makings of an epic tale.

Follow up idea: What if Clark decides the best way to out Luthor as the Boss is by remaining as Lex and destroying his whole evil-side-business? And then when Lex (as Superman) inevitably goes rogue, Clark-Luthor has to destroy him?

Probably not in-character, but that's how I like to party.

There's a time limit as Clark doesn't want to be stuck as Lex Luthor (despite being married to Lois), which he will be if Lex-Superman stays in the Kryptonite cage too long... and dies. However, if Lex-Superman escapes, he could then always expose Clark-Luthor as the evil boss, sending non-powerful Clark-Luthor to jail for Lex Luthor's crimes, while Lex-Superman is free to woo a heart-broken Lois, while being an all-powerful hero, who can literally take over the world.

This is a great idea... I love the creativity of it. And you could really do a lot with it. But trying to watch the scenes of Clark as Lex in bed with Lois would make my skin crawl (sorry).

Yeah, that idea churned my stomach as well, which is why I had that aspect as optional. Sometimes our minds can create worse images than a movie/tv show can.

Would Asabi notice the switch?

There is a Xander is costumed as Lex when the Halloween spell hits and ends up in the DC universe in Lex's head. Presumably Lex is in Xander's body. Only three chapters mixed in with a bunch of other story idea chapters. The writer is annoying that way, lots of good ideas and almost no finished stories.

From the third chapter after Xander has given Lex's body Plasticman's powers.

"Lex," Mercy said seriously, "I have some concerns."

Xander reformed the top half of his body, leaving the bottom half a large pink puddle. "I'm listening," Xander said seriously, sensing her disquiet.

"Your behavior has radically changed over the past few days," Mercy explained. "Not enough to activate the Doppelganger protocols, but more than enough to suspect you may be having your mind influenced in some way."

Xander completely reformed his body or rather Lex's body, making him look like he was in his early 20's and spent his spare time participating in bodybuilding contests. "Perfectly understandable, would an explanation of my current mindset help set your fears to rest?"

"Yeah, but that's also an example of a complete departure from your normal behavior," she pointed out.

https://www.tthfanfic.org/Story-30976-25/dogbertcarroll+Glittering+motes.htm
https://www.tthfanfic.org/Story-30976-31/dogbertcarroll+Glittering+motes.htm
https://www.tthfanfic.org/Story-32169-7/dogbertcarroll+Undulating+Flames.htm

Only if he's still in the picture. We didn't really see much of Asabi after St. John entered the picture. Maybe he's already started his occult shop.

I agree that does sound like a strange compilation of plots tied together.