The reason I would like a client certificate solution that worked (even if it was a malware target) is that I could reject all web traffic to my applications if

The reason I would like a client certificate solution that worked (even if it was a malware target) is that I could reject all web traffic to my applications if they came in without a cert. It would decrease my public footprint dramatically. I don't mind approving a user once per device. We've got to set them up anyway.