What you're describing doesn't sound like very good writing to me, Killing Dallis in Act 1 only reveals that you can't kill Dallis, and you can't kill Dallis because she is important for the plot later on, defeating her is also not necessary for the plot to continue, whereas the plot in BG3 advances with the great expectation that Minthara will be dead at it's end, either by people siding with the grove, or because you've rejected her sexual advances, or because you can't talk your way out of backstabbing her (DC questions aside) If they bring her back from the dead here, it'd be through another loophole deus ex machina that they need in order for a plot important character to be around for some reason, which doesn't seem to be the case nor does it sound like making choices that matter.
I also am seriously skeptical that the knockout functionality will allow for the kind of bifurcation you're hoping for, but as a way of putting a hostile Minthara at Moonrise Towers that you could potentially suborn into your quest, I'm open to, I just don't think that without the "heart to heart" that you have with her during the camp celebration, there is going to be that option.
