I do not think this is possible.
By design, once Impersonator impersonates another user, Impersonatee session was created as new smsession cookie, the old smsession cookie becomes SMSAVEDSESSION cookie.
When accessing a protected resource, the smsession will be checked or validated.
If you access Impersonator's original resource, you should get AzReject error 403 from poliy server, which means Impersonatee does not have the rights to access it.
You should always ends Impersonatee session before going back to Impersonator resource.
Hongxu