Inspired Hermit* Kick Rocks
By ignoring the central plot and not getting involved, the result could be both Halsin and Minthara (and most of the NPCs with 3 act content) somehow survive the ordeal, and when we come down from the Mountain we get to have Pity Party in the aftermath with the principles. Some pithy achievement like "Your Quest is Vain" but where we can wash our hands of most of the bloodshed without really losing out on either of the potential companions.
Inspired Charlatan* The Triple Cross
To pull this off the PC should have to lie shamelessly in their first interaction with Zevlor, Halsin and Minthara, tricking each of them with some opening misdirection. Here we set up patsies in each faction to take the fall for the stuff that we (the party) are actually doing hehe. Along this path maybe one of the bit players should go down, but only after they've delivered most of their flavor dialogue. Good candidates might be Brynna or Andrick, or the Aradin crew, characters like that. They should get a proper send off, but perhaps not at the Gates to the Grove since we've already seen that. Goal should be to screw over all 3 factions, perhaps via the Githyanki who we could also involve in the schemes, by telling them we've seen the weapon the seek and know right where to find it? Something like that. In this scenario most of the same characters die who would have died anyway if choosing one of the other standard paths, just in different ways here, but where the mains all make it out clean. The price on this one should maybe be losing a merchant or something more minor like that, but still allowing all the potential companions to survive through the first act.
Inspired Urchin* Goonies never say die!
The Tief kids home alone it into a scenario where Minthara is captured and locked up using a series of elaborate traps. Then she has to undergo a tribunal with Mol and the Owlbear cub presiding. Halsin should break in on this, amused at first, but ultimately intervening to prevent lord of the flies justice. In this scenario the Goblin kids also survive, and Arabella etc and it should tie in at that point with Halsin's quest in the Shadowlands, ie Minthara knows something about that, and so Halsin has more reason to keep her close. In this dynamic Halsin should use some sort of Druidic spell to remove Minthara's brand I think, and their initial thing should be like Halsin is taking responsibility for her. You know, like tables turned and now she's his prisoner instead. On Minthara's end, she should escape right afterwards, like that very first night, so she can be captured and sent off to Moonrise by parties unknown.
Just riffing hehe, but there's gotta be a few ways to make it happen that would still feel satisfying. It's fine if there are paths where there's like a 1 vs 1 break, but taking Minthara you gotta give up on 3 other companions. I don't know that I necessarily need Halsin and Minthara to end up compatible, but it'd be fun to see it drawn out with more options.