When creating a custom role, I should be able to inherit from one of the existing built-in roles. The built-in roles change through time as new features come on board, so simply copying a built-in role at one point in time doesn't really help. We created our own custom code module that reads all the permissions out of role and then write them into a new custom role where we can then append or remove additional permissions. Our custom roles are then totally recreated in batch in night to keep them in sync with the latest changes to the built-in roles. This pseudo inheritance works really well for us, but it would be much better if this kind of inheritance for custom roles was built into the platform.