I have this idea, and I have no idea where in the story you would do this, but I had the idea of Y/N would temporarily leave the MHA timeline and return to the time nest, and while he's gone the heroes would get a report that pretty much everyone in this city is gone near me, missing. No one knows where they are, so they go to investigate, and they find Imperfect Cell there. And he would absolutely terrify them, instill a fear of them that they had never felt before, especially after seeing him absorb someone, and I don't even know how they would even survive the encounter, maybe Ekon would rush in and help them but Cell would escape.
And every time he absorbs someone from the MHA world, not only would their quirks make him develop at a faster rate than in the original timeline, but he would also get all the quirks of everyone he's absorbed. The idea I'm generally thinking of is not only would the improved energy from the people with quirks would make him stronger, like maybe the after absorbing enough people. His imperfect form is on par with his perfect form. So that when he reaches his perfect form, he's on a whole other level than it originally did. But it would also give him an even greater level of versatility, with all the different quirks he's absorbed would also be stronger, given his superior body.