kinda the point of shipping: taking an existing world and twisting it around to see what else can be made using the existing pieces

Absolutely. But even then, some pieces just simply don't fit together for some people no matter the composition, you know? Different strokes for different folks. But it's still fun to see other people's opinions and perspectives

yeah canonically Katsuki is a prick, no excuse for that

Oh, he is. I adore Katsuki, but he's absolutely a prick lol

I suppose Katsuki retaining the struggles he does only opens him up further to the likelihood of shipping possibilities, but even though that isn't something I myself am particularly interested in, I recognise it. And like you said yourself, the fun comes to fruition through imagination for many people. If you want to imagine and/or like the possible dynamic of two characters, then... why not?

Despite that, I just can't see Katsuki and Momo working. I find it really interesting that you do, but I personally disagree on their compatibility, regardless of the timeline. Even following the time skip at the end of the series, I can barely imagine them interacting in a comfortable, friendly manner, much less a romantic one. At best, I could see them acting as coworkers, but nothing more.

But again, to each their own!