The following question How to develop and optimize the illusion of meaningful character development between the player and NPCs? [on hold] will be deleted in 24 hours.
I request some ideas on how I can shrink the scope of the question to make it on topic. I agree with DMGregory that the question is academic and their may not exist a simple recipe answer. I believe that this post will prove valuable for many developers down the road, because as Extra Credit has stated, this is a current issue that has high demand for advancement and implementation.