I think Marvel should make Shang Chi as much like Bruce Lee as possible. Don't shy away from the original inspiration. Give him many of the same characteristics and even the fighting style. Let him use things like Nunchakus and even the Bruce Lee high-pitched screams.
Imagine if you were watching Enter the Dragon but then found out it was actually a Shang Chi movie. They should do something like that. In fact, it should be as if it were a 6th Bruce Lee movie that we never got, almost as if it were a lost Bruce Lee film that has only been discovered.
I think this film could have widespread appeal beyond just comic book movies if done well. If it's a good martial arts movie in its own right, then it could have universal and long-lasting appeal.