Am I correct in thinking that the reason it's not there is the same as for database enrolment?
ie. the plugin is designed along the lines of 'when you use it, the users will be added automatically' and there's an assumption that no further fine grained control is needed?
We also notice that when you disable IMS Enterprise enrolment for the whole site (site admin->plugins->enrolments->manage enrol plugins) user previously enrolled via IMS enterprise are hidden. So we have to keep the this turned on all year (adding to the cron load) making sure there's it's set up to point at a blank file?