I don't think HB is saying they are Morman just that they might follow the model where guys have two wives even though legally they are only allowed one.
I'd imagine this game will have to have at least 20 endings. I don't think it's impossible for some of the B and C cast to have endings, but I doubt they will get 'happily ever after' with the MC, but I think as it stands you can reasonably look at the chances of a complex ending like this;
A - Jill, Isabella, Josy, Maya, Sage, Quinn
B/c - Camilla, Riona, Jade, Cathy, Ahsley and Mona
C/D - Sarah, Melanie, Heather, Elena, Nicola, Sally, Lily
Basically the lower in the order the chances of a complex ending decreases. Heather and Elena are probably tied to John Boy and Tommy. It's all quite complicated, but essentially the main 5 LI's are likely to have the most time spent on their endings