I think there is an important challenge in making the distinction between complexity and security.
Some people still believe that added complexity increases automatically security.
This belief should be erased. We should keep on working towards secure and simple systems, that are as easy to understand for the people as a door lock, a sealed envelope, etc. Not only because more people can look at it, but, more importantly, because the model forces people to write more clear code, and to adhere to standards. This in turn facilitates security reviews. No library code should be required for the packing or parsing of SPKI certificates.