Customers want to be able to create new channels from a Jira ticket, rather than Mattermost. For this, we'd have to write our own Jira plugin.
Want to assign a ticket from Jira creation screen. Herzum has a similar tool on Atlassian Marketplace. Create a plugin in Jira where I can from a Jira issue page allow my users to select a channel that issue should post to.
This was a loved feature from hipchat for my users.