Allowing non network admins a task reserved for only super admin status.

We want to allow a specifically called out category say author to be able to create sites..

Understood this role is spelled out for the super admin .. We are using blog template create plugin ( so template are available as this plugin provides)and want extent this one function to (in this example authors)..

We want to limit authors to normal function + this one additional capability..Not turn them into super admins