But this WILL actually work for the most people. Even the range of officially recognized LIs is much wider than in most very good story games. If each of them gets the same amount of screen time as Bella and Nami, then those who don't like any of the official LIs will be the black sheep.
If you like milfs - here's Amber and Marla, you like redheads - Nami and Nia, huge boobs - Mila, Vic and Nadia, aggressive girls - Bella and Zara, a little nerdy - Nadia and Sonya, evil bitches - Bella and Vanessa, quirky - Nami, Nia and Vic to some extent... You can go on and on, you have to be uniquely picky to not find a girl to your liking with such a rich choice.
Well, there will always be guys who are longing for Karen Rebecca Johnson, despite all the possible options.
EDIT: Oh yeah, and I forgot that I learned today, if you want a mystery, then Sasha.