In jira you have only 3 levels to model your project system.
So for our business projects we used:
jira projects to model programs,
issues for projects
and sub-tasks for project tasks like business requirements

The ability to create jira sub-tasks in confluence would be very usefull,specially for large projects, since we create requirements documentation in confluence and we could create the requirements fastly in jira as well without leaving confluence.
Thank you