One mad modder has already gotten Baldur's Gate 3's semi-secret 'evil' companion working in good guy playthroughs
Enemies to lovers arc.
Modder Rukongai over on the Baldur's Gate 3 Nexus seems to have cracked the code on Drow Paladin Minthara, with a pair of mods making the Grumpy Gus companion recruitable without committing a war crime in the game's first act. One version makes her normal Act 2 storyline play out in a more heroic playthrough, while another makes her summonable as early as Act 1.
Minthara placed dead last in our ranking of BG3 companions, but I'm pretty sure it's because none of us actually recruited her. Befriending Minthara instead of just killing her for her Spidersilk armor and nifty pajamas requires aligning yourself with some pretty heinous little goblin sickos, and this choice also locks you out of other companions like Karlach and Wyll.
That's tough to swallow, but also part of what makes Baldur's Gate 3 so special: that two playthroughs can look so completely different from one another. Still, Rukongai's mods can be a valuable introduction to Minthara for queasy-stomached gamers who only experienced her as an early game boss.
As a warning, this seems like far from the way the game was "meant to be played," and both mods have compromises to get them working. Minthara doesn't have dialogue or interactions with characters she was never meant to be in the same party with, for example. There's also not a perfect way to get her into your party on a good playthrough.
The "Good Recruitment" version feels more natural, just making the Drow Paladin show up where she usually would in Act 2 after aligning with the goblins, but locks you out of Minthara's first romance scene, which takes place at an evil goblin version of the party at your camp in Act 1.
Rukongai's original version of the mod lets you access that scene and have Minthara in your party as early as Act 1, but this requires some special magic item intervention, and Minthara also doesn't have dialogue or reactions for Act 1's various quests and events.
Still, it's an amazing bit of work that Rukongai got this functional at all, and so quickly after launch to boot. Larian's also got plans of its own for Minthara: The game's next big patch is set to restore 1500 lines of her dialogue previously cut off by a bug.