Mark Fields on Forms "Internal Only"

We want both internal and external users to use the same single ideas portal. However, if internal employees are submitting ideas we would like to ask additional questions. Currently this would require two separate idea portals with 2 different forms.

Ideas already has logic around "Internal" or "Aha User" under the visibility settings, however the forms do not have this functionality. It would be great if on Ideas Forms we could mark a field as "Internal Only" - this would mean only internal users would be prompted for the field on idea submission, and also if the field is set to be displayed in the ideas portal it would only be visible to internal users.