i've started development of the node relations module, i called it nodefamily module.
As the module might be useful not only for profile nodes, I've written it generally, so that it may be used without nodeprofiles at all.
It allows you to define relations between content types. It uses this relation to automatically mark all nodes of these types of the same user as related. For this it uses its own simple API for node-node relations.
Further it lets you define a number of maximum nodes of a content type per user - quite useful for nodeprofiles.. ;)
I've also already created a simple nodeprofile module, which allows you to mark content types as user profiles. The nodeprofile module uses the nodefamily module to set the number of maximum nodes of nodeprofile content types per user to one. Further, if the usernode module is present, it adds a relation between the usernode content type and the nodeprofile types.
So it should be possible to build nodeprofiles, which may consist of several content types - hold together by the node relations.
The usernode could be used to provide an overview of all profiles, or for displaying all profiles...
I don't concentrate on creating a superior way this all should work, I would like to create a flexible solution, which can be customized easily.