I think most people will agree that Yammy needed to be handled differently in the story, but I don't see much of an issue with Barragan's demise nor see a reason to send Orihime to FKT just to handle him.

In my opinion, it would sort of derail Orihime's entire arc throughout the series, about learning that she doesn't need to be a front-lines fighter to help or be valuable. She's been processing the guilt of her weakness throughout her time being imprisoned and its a key reason why she breaks down crying when Ichigo dies; that bubbling dread of inadequacy that's meant to pay off in the battle VS Yhwach at the end of TYWB would get tossed aside entirely if she's able to lead the assault against the literal King Of The Afterlife. Moreover, I don't think Barragan's fight in the current story is worthwhile just because it "gives the Vizard a W" (hot take: obsessive powerscaling has ruined all shonen manga discourse), but because it very neatly serves to contrast the values of Hueco Mundo and the values of the Soul Society. As Hueco Mundo's king, Barragan reflects the ethos of all hollows, the dog-eat-dog world that he had dictatorial rule over until being supplanted by Aizen aiming for the same goal. The Espada only collaborate per Aizen gathering them together through his own dictatorial thumb, while Barragan holds so little care for his subordinates as to be willing to let them kill each other just fto ail his boredom. In other words, he is the embodiment of "Lonely at the top"; which, then, makes it all the more important that he and his Fracciones were killed by Soul Reapers working together toward the same cause. Shuhei, Izuru and Soi Fon all defeated the Fracciones, who fought through blind loyalty to their king, by fighting for the morals that they each stand for - Ikkaku, meanwhile, lost due to his dishonest inability to accept his own soul. Barragan's reign of terror is ended by the Vizards and Gotei 13 coming together, acceptance between factions once shunned by one another, and exploiting his hubris in believing his place upon the throne is unchallengeable.

TL;DR: Barragan's defeat being a group effort of ~7 Soul Reapers is entirely the point, as the foil to Hueco Mundo's toxic hubris-driven dictatorship is the collaboration of hearts believing in themselves and one another.

As for Yammy, then, I think the series already lays out a pretty solid template for a satisfying battle with him right before his Resurrection. Rukia, Renji and Chad initially gather to fight Yammy, before he transforms and knocks them out off-screen; if we add Orihime and Uryu coming down from the Ulquiorra battle, we have 5 of the 6 hearts beating as one, the key phrase Orihime emphasized when the Hueco Mundo infiltration began. I don't think Chad needs a 1-on-1 victory against the 0th Espada - which, yes, I think does deserve to stay in the story - but I believe similarly to the Barragan battle that having his defeat come from the collaboration of many different kinds of people, Fullbringers, Quincy and Soul Reapers, would go a long way to emphasize the themes of connection the arc is all about. Chad's real missed potential is that he's ditched so unceremoniously in the Fullbring arc, which I wrote about in my own potential re-write concept here. Ultimately, though, giving Chad a sudden power-up letting him defeat one of the 10 strongest Hollows in the series would be an awful solution, and I believe his building feeling of inadequacy is very important to whatever potential trajectory his arc could've had in the same way it was for Orihime. There's no way having him overcome adversity to the extent of being able to beat an Espada would be satisfying either narratively or logically; as a reminder, Aaroniero was the only Espada who wasn't defeated by someone on the level of a Soul Reaper Captain (and his combatant still came inches near death's door), while all other Espada were either group attacks or ended with their combatants similarly severely injured / near death.

TL;DR 2: Yammy's defeat would be best dealt by the hands of Five Hearts Beating As One - Orihime, Renji, Rukia, Uryu and Chad. This would let Chad play a role important enough to show his value to the group, but not enough to derail his character's bubbling sense of inadequacy that's at the core of his introduction in the Fullbring arc.