OMFG. THE REASON KIERAN MAY HAVE BEEN POSSESSED IN TEAL MASK BUT NOT POWERFULLY INFLUENCED LIKE CARMINE AND THE NPCS IS BECAUSE THE MYSTICAL PECHA BERRY RE-AWAKENED PECHARUNT. AT THE TIME OF KIERAN'S "POSSESSION", PECHARUNT WASN'T AT SAY, FULL POWER YET, HENCE WHY WE ONLY VAGUELY SEE PURPLE MIST WHEN HE PUNCHES THE SHRINE.
Since Kieran wasn't possessed by Pecharunt after all...there is still a chance we could get that storyline. Thought at this point, Kieran is on the way to his full-redemption (he still has a way to go).
But when the event for Pecharunt is released: What do I think would be interesting? If Pecharunt ended up possessing Drayton instead
This would be very interesting for the duo's dynamic. Drayton spent every encounter with Kieran purposefully trying to get under his skin and was absolutely brutal towards him when he'd just lost against us, and Kieran seems to actively despise Drayton at times.
After defeating the DLC, Drayton mentions that he's glad Kieran seems back to normal now, and he'd thought things would've have been patched up between the two of them by now, but they're just not there yet. Drayton actually wants to be friends with Kieran and says he wants to battle with Kieran again, even though Kieran has rejected his Blueberry League rank entirely.
That leads onto the Pecharunt storyline. As with Area Zero, if Pecharunt appears in the Terrarium, Drayton and Kieran could be the ones sent to deal with the fallout. They'd have to work together, which could lead to them finally hashing things out, or having a fight over everything that's happened.
But what if Pecharunt is gunning for Kieran, but Drayton pushes him out of the way and gets taken over? Or Drayton could just get unlucky and be the one Pecharunt chooses? Or he's silent and literally puppeted around? (It's giving Nihilego & Lusamine vibes). Either way, Kieran sees Drayton go all crazy and has his epiphany "Wait...is this what it was like when I went off the edge?" and realises he has to save the other.
Or maybe this is all just cause I think Drayton should get to go a lil feral. As a treat. Anyway, I just think we need more lore and interactions when it comes to these two together.