Hierarachical versioned components, with cross-referencing

What is really missing from JIRA from our point of view is to be able to create component hierarchies within a project and to version components rather than an entire project. In addition, a component in one project should be able to be 're-used' in another by cross-referencing to that components project (the one in which it is really managed and developed). If this were implemented we would also like to be able to indicate version dependencies, and generate compatible version graphs, etc.