Documentation for administrators on how to generate codes would be necessary. A backend interface to manage generated codes, view statistics, etc.

Testing would be important. How to ensure that code generation works correctly, that the validation process is robust against invalid inputs, and that the security measures are effective.

Testing the code generator and validator thoroughly is essential. Unit tests for code generation that produce valid codes, and validation tests for various scenarios like expired codes, invalid signatures, etc.

In summary, developing a secure, user-friendly registration code system for BetterWMF 6.0 would involve designing a secure code structure, implementing robust validation logic, creating administrative tools for code generation, and ensuring the system is resistant to tampering while providing a good user experience.