To be honest, it’s really hard for me to comment on this issue because I don’t know how the C/C++ layer of blender works. However, the only comments that I’d make are:
(1) Give the python api as much access to the underlying C/C++ data structures as possible. If there is something that can be done through Blender GUI, it’d be nice if it could also be done through python.
(2) Make the api as stable as possible. It’s rather frustrating when a large number of your scripts stop working when you upgrade to the next version of blender.