See, I have a 10 user JIRA license (for personal use) and I'm trying to get a better understanding of the entire software. Currently I'm going through their documentation (slowly but surely), but (a bit off topic) do you happen to have any faster-to-understand documentations? The current ones are pretty dry and takes up way too much of my time getting into every single detail (currently I don't have too much time and it'd be awesome to use this system to help with my current situation).Personally don't think JIRA will work with a WHMCS environment, especially looking at the costs beyond 10 users. If you're going to open up the roadmap etc, it'd be good to let users comment and provide feedback.
The JIRA interface and how things work is also vastly different from WHMCS. To get user management synced, you'd need a custom Crowd authenticator and need Crowd.