Just manage the points for the other LIs and they'll never approach you out of romance. There are certain overtly romantic choices you can make that either lead to love interest, or friend status. You can do it with Alexis, Erynn, Layla, Val, Niki, and Cara, for sure. If the points get too high they'll approach you. But if you don't go over the 'threshold' you'll just become (best) friends and they never express interest in you. In addition don't flirt or do anything overtly romantic and it won't trigger anything.
On any playthrough I can keep them all from wanting to, or asking, to date the MC.