I agree, IMHO, Rachel should never be considered...
There is an old saying for guys among each other: "Never stick your dick in crazy."
Rachel is clearly crazy. Her whole character is devoted to fighting the patriarchy and the founding families. She clearly sees herself as a crusader in this war and will NEVER bend to any reality that even slightly deviates from her preconceived fiction. She is a religious zealot in her own world.
Rachel has lied, stole, made false accusations, and manipulated people to obtain false evidence. How can she ever truly be on "Team Fletcher" when her only goal in life is a fanatical pursuit against the patriarchy?
Just how far would she be willing to go? Would she plant evidence, photoshop pics and edit videos? How about poking pinholes in condoms or replacing birth control with placebos? These are things she would likely consider on her own; if she ever got close to the MC how quickly can Gloria Russel bribe her to do these and worse? (And remember, Gloria Russel is the one family head that is not part of the patriarchy.)
Another thought is long term... If Rachel ever had a daughter with the MC, how soon would she run off with their daughter to "save" her from the patriarchy.
Simply put, Rachel can NEVER be trusted.
Even if the MC is only thinking with his lower head... Assuming Hannah is a girlfriend at the time, how could Hannah forgive Rachel for stealing he lottery book and taking a picture while in an intimate moment with the MC? Hannah should blacklist Rachel from the potential GF list.
And then there is Alison. Alison warned the MC of Rachel early on. Alison even said the no poster rule in school was created specifically to stop Rachel. She knows Rachel is insane asylum level crazy. As the MC's advisor she should slap sense into him for even considering Rachel, not to mention also blacklisting Rachel if she is the MC's girlfriend at the time. If Alison can't convince the MC to never trust Rachel, it undermines all her credibility as an advisor.
Mind you, other than Lucy, all the LI's had some level of secrets and manipulation toward the MC; but, none of it was even close to the level of BS he has dealt with regarding Rachel. And that was before the story brought up the MC as a founding family member, which would make Rachel despise him even more. Rachel may be hot for him, but she will never really like him and that disjunction can easily be explained by the fact that Rachel is Batshit crazy.
