It's difficult to make an important set of projects inside a single instance of Jira correctly set and managed by a single administrator.
It would be interresting to be able to delegate configutation of a subset of Jira elements and projects to a specific adminitrator, to isolate more completly a project from one another concerning configuration elements and to be able to trace administrative actions of the administrators on remaining shared components of Jira if such components still exist.
This would make Jira more usable in big organisations.