I've had two similar ideas that do very different things, and I don't know what to do with either of them. So I'm going to toss them both over here. (I'll write out a bit of one, and the other can remain as a one-sentence premise.) Feel free to pick up either or both and see where it takes you. But, considering the nature of things, maybe one of them should be a round robin?
Premise #1:
"Is everything ready, Nigel?"
"Yes, sir. Mrs. Cox assures me the flowers are in place, the caterers are ready, the archbishop is -"
"That's not what I meant, Nigel."
"Ah. Yes. The cage is complete. However, we were only able to procure a small amount of kryptonite. We had to powder it and mix it into paint to coat the entire cage. That leaves us with only this piece remaining."
"It looks odd."
"Yes, sir. But the wavelength matches. It is kryptonite."
"Hmm. I don't like leaving things to chance, but we have the cage ready. Very well, we'll use that piece here."
--
(Actually, I'm finally ready to try to get back to sleep. So I'm just going to summarize. Lex lures Superman into the basement. This time, he's standing there personally. Superman zips over and hoists him into the air. So predictable. Lex presses a button and a red K laser fires. But it doesn't have the expected effect. This is much better. Superman staggers and drops Lex, but Lex floats above the ground. He grins. So much better than his VR fantasy. Who knew it would turn out to be good training? No need for the cage now. It probably wouldn't even work on him anymore. He flies off, leaving his powerless enemy behind.)
Premise #2: The red K laser is created later than we saw in the show. This time, it's Wanda Detroit who becomes Ultrawoman.
Make of them what you will. Have fun. I'm going to try to get some sleep.