I'd rather not go through the process of getting more domain accounts created, is it possible to install a new TFS instance using the same service/report accounts as another TFS instance on the same domain? Are there any drawbacks with doing so?
Non that I have encountered as of yet. There is the obvious security issues but they aren't a concern for you than it is fine to do so.
We have two instances and everything is running fine.
Hope this helps!