Jira needs sub-components, sub-projects, products, or suites.
A product suite is composed of several projects. A project can be included in multiple product suites. A product suite has versions and each suite version is tied to specific versions of its contained projects. For example Suite 5.2 might contain AppX 1.2, Core 10.4.1, and CoreUtils 9.3.1.
I believe that the product category concept could be extended to behave more like a suite. Add versions to categories, allow a project to be in multiple categories at once, and then allow linking of "suite" versions to specific project versions.
Alternatively, just allowing n-level nesting of projects would do the trick and would eliminate the need for components altogether (as noted in JRA-846).