So, can you point out to me where you are getting the information that it can't be done?
What, are you insane? Don't confuse the issue with facts.
Apparently I am since I forgot that Chandran sigs are in fact "Sub-linear Ring Signatures Without Random Oracles" and I found a paper that shows how to make them traceable etc. Not to mention a few papers that offer improvements and/or alternative methods to that paper. lol