If I remember correctly, Fujino didn't plan to do a cuck-route initially? To be honest, I still can't imagine how you could implement it properly in this story, aside from just without reason.
For that, he would need to split the story, perk and stat development at some point, but until now, there is literally no buildup to that. Yeah, you get some cuck-points for watching other people, but watching other people is not the same as watching your LI, so idk.^^
As an ending, I think something like Kirito never figured out why Asuna broke up with him and just went abroad alone and frustrated. End of story
But I don't give up on believing in a Sugu-dom ending.