Optional routes in a terms of an optional girls? You did a vague term description.
I'd not suggest it. This optional girl can be loveable, and if she will lock with an (for instance) BDSM route, it means the guys which against DBSM will not able to date her.
To make it work (like, really) you will have to make two routes for this one girl (one kinky route and one classic, "vanilla"). And if you asking just this - should you making two routes (for players can choose) - than yes. This is your solution, and it will cost you double work on this, but it will pays with LP flexibility and appreciation by more players.