@ARTEMlS:
It'd be a copout on a narrative level. Sure, Luffy is about elasticity and Kata is about viscosity or whatever. Of course, they are different in some ways. But what Oda told us here is that there is this dude who can perform everything that Luffy can, but just better. EVERYTHING. I don't want to see Luffy winning this by just performing some fancy attacks which Kata cannot counter at all. That would not be everything. Considering that this actually is the first enemy of the kind who Luffy has to fight (not counting Brulee as there wasn't a real fight), I actually want it to be a REAL mirror match. Where Kata really can counter everything Luffy throws at him in some way.
As for the solution to win this for Luffy: No G4 dominance, no G5, no awakening… No, just no. Nothing that Kata just cannot imitate. Instead I expect something more creative from Oda, like Luffy adapting his fighting style to the actual mirror situation. So Kata is stronger in everything, right? How about some fighting technique then that gives Kata his own medicine right back in the face? And Luffy "only" has to tank his own punches? Anything like this... but just no easy breakout of the mirror routine please!
Oda didn't tell us that. That's merely what the characters observed. And besides the Straw Hats, who are they to accurately judge how in-depth one's powers is similar to the other's? It's only a shallow judgement. So when they say "everything", I take that with a grain of salt because we still don't know certain things without seeing them visualized. I personally wouldn't mind Luffy winning with certain fancy attacks that Katakuri can't replicate so long as those attacks already exist (like Gear Fourth) or are intuitively created from Luffy being inspired like the good o'l pre-timeskip days up to Skypiea.
But I get what you are trying to get at. A premise was established in readers' minds that Luffy and Katakuri can do everything similarly, except Katakuri's versions are superior. And you want to see how Luffy can overcome that premise without cleverly subverting it. I understand that. It can still be entertaining in its own way.
But how can Luffy give Katakuri back his own medicine? Katakuri can, at least right now, do everything Luffy can do AND MORE. He can make weapons. Snipe with jellybeans. See the damn future. Make mochi earplugs for everybody to block out sound. Make people or things to stick to him. He can become intangible to attacks like a Logia. He has a water weakness buffer, but that hardly matters when Jimbei isn't around and I doubt we're going to see the "my blood is like water" twist again (and I wouldn't want to see it again). Have we ever seen a character with such a ridiculous repertoire of stacked separate abilities in One Piece thus far? He's giving Sugar and Law a very good run for their money and almost sounds like a pretentious fanfic character trying to give Luffy an epic dark overpowered counterpart. Sorry, but I'm not into Luffy's powers being so pathetic that there can't be anything unique to him as well. I hate this ridiculous Devil Fruit supremacy concept that's come up ever since Marineford, it's so uncreative. The only thing about Luffy that stands out is his blunt force immunity and compression/bounce abilities, and I want to see those brought into the equation.
If Katakuri was limited to mostly just being a superior Luffy, I could agree with your desires. But tolerating all of that and accepting that Luffy can never stand out well? Screw that. You and I both know there is no way rubber can mirror any of those things unique to Katakuri unless he awakens a very quirky Awakening, and we both don't want asspull power-ups gained from frustration in the middle of a battle.
However, I get what you mean now about the mirror idea being scrapped now. If Luffy's Gear Fourth can't be replicated and he wins or stalemates with that, then what was the whole point of hyping up Katakuri to be a mirror of Luffy? It would feel like a waste of time and of a potentially cool battle concept. But I feel like if we stick to that, then the only reason Katakuri loses is because of not being able to predict Luffy's plans. If he could, he would most likely be able to replicate and counter that too if they were to ever have a rematch. Which would make me feel like Luffy only got lucky and is still inferior rather than how he can actually stand out on his own and not have a power that completely sucks compared to another Devil Fruit.
I think the only way this battle can really appease us is if Luffy can eat Katakuri like he did with Cracker lol, but it's difficult for me to imagine all of that sticky kochi not suffocating Luffy.