Control Groups / CSIs

Our Accessibility team would like to have a new Activity Type added that only their user group has access to add.

Which I know could be done with Control Groups, except that they would like all other users to have visibility to those CSIs once added, just not the access to set them up initially.

I tested it out, but, as expected, locking down the Activity Type by Control Group prevented anyone outside that Control Group from seeing the CSI at all.

Has anyone figured out a way to lock down add access to something as specific as an Activity Type without removing view access from everyone else?

Thanks,

Shelly