Just to be clear: you'd like the ability to for a primary system administrator to allow additional system admins to impersonate users on some domains but not others? Just asking for clarification as there's already the ability to manage impersonation as a whole when adding a new system admin. 

To be honest, that seems like a level of granularity that just complicates things, but if I understand you correctly, I'll add the feature request. 

Yes I understand there is the ability to turn off impersonating across the board for admins. But there are some domains that only the primary admin can impersonate. For example, I don’t want my employees to be able to access my email as the owner of the company. Or if we were hosting a high level customer like government or celebrity.