It's wild how a single headcanon can reframe an entire character, isn't it? With Kaeya specifically, him being the 'bottom' in a pairing, especially with someone like Diluc, flips the power dynamic we see in-game on its head. Kaeya's always portrayed as the charming, in-control manipulator, the chess master. But writing him as a bottom often explores the vulnerability beneath that. It's about him letting that guard down, the calculated flirtation becoming genuine need. The romantic tension doesn't vanish; it transforms. It's less about who's chasing whom and more about the push-pull of trust versus control. He might still initiate the verbal sparring, but the physical or emotional surrender holds all the charge.
That shift makes the eventual catharsis hit harder, I think. When a character built on secrets finally allows himself to be truly seen and accepted in a more submissive role, the emotional payoff for the reader is immense. It's not a reduction of his character; it's an amplification of a hidden facet. The tension becomes about whether he'll allow himself this softness, and if his partner can handle the weight of it. It turns the typical 'enemies to lovers' trope into something more psychologically intimate.
I've seen it done really poorly, where it just makes him seem weak or out-of-character. But when it's done well, it highlights his complexity. He's still cunning, still sharp, but he's choosing where to lay down his weapons.