So after running through this again the process of extending the Windows 2000 AD schema for TAM ESSO is a bit more quirky than I thought. It certainly works and the TAM ESSO product functions as designed afterwards, but you have to jump through one hoop first:
From the TAM ESSO Admin Console click Repository -> Extend Schema
Next, choose Microsoft Active Directory as the Repository Type
You will see this error message. Notice that the error occurs after the line "Adding Attributes". If you click Close and then go and view the AD Schema with MMC you will notice that just the 5 new v-Go attributes were created. The classes were not.
Note: If you choose "Microsoft ADAM" in this step instead of "Microsoft Active Directory" the operation will fail with an entirely different error and neither attributes nor classes will be added to the AD Schema.
Now, go back again and click Repository -> Extend Schema
This time choose Microsoft ADAM as the type.
This time you will see that the operation was successful. Now if you view the AD Schema with MMC you will see that now not only do the 5 v-Go attributes exist, but also the 4 v-Go classes. Any further operation proceeds as normal.
Even though there are not too many organizations out there still using Windows 2000, there are still some. I'm not sure what IBM's road map is for continuing to support Windows 2000, however currently they claim to support it with SP4.