i get that some people dont like Korra, but come on mates, you all know that she IS the main girl in this chapter, no amount of "i dont like her" will change that. unfortunatelly, if you hate her SO MUCH that it hurts physically that a fictional character dicks her, then maybe it would be best to skip it. i say this as someone who(belive it or not), actually dont like incest, and just didnt play book 2 LR, even though i enjoy LRs much more than SRs.
as for who could be the MC, there are a few characters, i doubt it will be tenzin again, and i seriously doubt it will be korra herself either. the best choice would probably be a new custom character. no need for backstory, is able to dick anyone without compromise, and the story can go anyway they want without the need to stick to anything.
either way, i think they should talk about it as soon as possible, since they will need alot of thought as to not screw this one up(like they did this last SR)