As JIRA Administrator, you are allowed to delegate the Create User operation to powered users, by using some custom Permission. Also, powered users will be allowed to create new users (Only Create ...).

User Creation Permissions

This plugin provides some custom permissions dedicated to Create User operation based on JIRA Applications. All of theses permission allows powered users to create some new users.

They only differ on the Application scope

Application	Custom Permissions	Descriptions	Since
JIRA Core	Create Core Users	Allow users to Create a new User, with, optionally, an access to JIRA Core	for JIRA
JIRA Software	Create Software Users	Allow users to Create a new User, with, optionally, an access to JIRA Software	for JIRA
JIRA Service Desk	Create Service Desk Users	Allow users to Create a new User, with, optionally, an access to JIRA Service Desk	for JIRA
None	Create Users	Allow users to Create a new User, without access to any JIRA Application	for JIRA to

How to process ...

As JIRA Administrator, you will process as follow :

Go to a Project Permission Scheme, and edit it,
Grant users to one or more of the custom permissions Create XXX Users.
Let these powered users to access to the feature.

Reminders ...

Note that :

Even if a JIRA Application is not licensed, the Permission will provided, since there is no way to condition Custom Permissions
Powered uses will be only allowed to create users, but not to edit their details (perhaps in future version) or delete them.