What your post made me realise is that data such as access data don't necessarily have to follow the class structure of objects themselves. So, for example, whilst objects of class Node have access data of type Access::Node. Its subclass Node::HTMLData doesn't have to inherit its access data from Access::Node (although it could), perhaps its access data could come from Access::HTMLObjects.

Perhaps you should look into Roles for this. They make it very easy to address cross-cutting concerns like this by using their more horizontal composition style. This approach also tends to help prevent the typical OO explosion of subclass trees where you need to subclass an entire section of your class hierarchy to just extend one node of it, sometimes called the Expression Problem.