Alright so i believe that you should add shield support to minecraft so you can make custom shields. i dont know if this is a feature already present but i believe this would be a great feature to add if its not. thanks for your time
~Shino
Issue comments
I have checked and shield and elytras can't have any custom properties so, for now, we won't add this, but will consider adding this later on.
There are other features more important right now that do not require that much code rewritting so this is currently considered out of scope.
We have this feature on our TODO list. This feature will most likely be added in 2.x.x branch.