As for non-incest/pure father, i'm in general always in favor to make any LI optional/avoidable. But as she is pretty much the main girl it would probably a lot of work to do so, not sure if it is worth the effort.
This is not about making a LI optional.
What I mean is that by offering the player the choice, you increase the taboo.
The forbidden fruit.
The more innocent and pure Kailey is, the more the MC would want to protect rather than corrupt her. By corrupting her, he would be corrupting himself. But he already hates himself for his porn addiction. Corrupting Kailey would make him hate himself even more. If this were a childhood romance story, there would be no corruption, it could just be pure love. But in this case, with the MC being married, the difference in age and experience, not to mention the incest, well...
Is there a way out?
Could there be a good ending, like in Triangle? Justine seems kinky enough to go for it, once she gets over the initial shock.
Or would the good ending be that the MC keeps it in his pants and let another worthy guy or girl romance Kailey?
When there is no choice how to approach this dilemma, then the taboo becomes meaningless and empty. Like in a FPS game, shooting hordes of zombies is meaningless, but if, when you are close to the end of the game, your best friend turns out to be aiding the enemy and you get to choose to shoot her or let her go, then that is meaningful. Even more so if she returns at the very end of the game to help you or to complete the betrayal.
Before someone cries some dreaded 3 letters, this is what's supposed to happen to fathers and daughters, you fucking perverts
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)