The ideal place is already built. Reaper, the other author who made a branching plot has already made a very less-NTRish more vanilla/harem heavy story. The dev just has to adopt that and will be fine.I'm replying to these a few months late because I just read the story and have been contemplating this very thought.
The ideal place to fork the story onto a non-NTR path would be to either have Amelia convince the MC to merge their group into Jax's group or to ask his mom to take over the training of their group so Amelia doesn't have to leave their group to join Jax's. It's kind of stupid that the MC refuses to train with either Jax or his mom (his mom is the most powerful adventurer in the village while Jax regularly trains the village youth in adventuring) after acknowledging that they'd progress faster with real training from real adventurers. He then just sits back complacently and let's his childhood crush leave their group to join Jax's group without him where she gets to grow increasingly close to Kase and the NTR starts.
It's doubly stupid that after rejecting his mom's offer of training because he doesn't want to impose on her time, he actually pushes his mom to train his rival Kase when she was initially planning on turning Kase down. So his taller, richer, more skilled rival gets training from both adventurers and gets increasingly close to both his crush and his mom while the MC...goes fishing. Uggh. That's crazy cuckold porn logic and an example of theYou must be registered to see the links.
He already get 2 different branches to make it into game.