The real question is who would be the main love interest in the series? I imagine it would be Sage or Jill with Sage being the more likelier due to her proximity to the diks and her Chad storyline opening up a whole lgbtq storyline which would be appealing nowadays.
Incredibly, the girl that probably has the most ammount of content regardless if you are in her route or no is most probably Quinn. We saw countless flashbacks of Rox and what he meant to her. We also saw her scheming with Riona, with Lily and with Tommy a lot.
But being the main girl? Nah, Quinn works better as a tritagonist of sorts. The series would just need to make MC interact more with her to create conflict.
Maya and Josy are perfect to NOT be main girls in such a series since they are a couple already. The MC would fool around with them, but will discover their relationship and choose to remain friends.
Bella is plausible, but difficult and she also fits very well as a support for Jill.
Which leaves Sage and Jill and if we follow BOTH their routes in the series would be amazing. Perfect drama, it could also show that Sage dislikes Jill a lot more during the begginning of the series, but comes around when she founds about her hate for Tybalt.
I can't choose either since both would be amazing. Closely followed by Bella and then MaJo and Quinn would actually be tied.