I don't think it is "hard" to do, technologically or otherwise. Or particularly expensive. I mean, I guess it could be financially unworkable if, because of other content, an extra audio track wouldn't fit on a DVD (I wouldn't imagine it being an issue with BR), which would then necessitate an additional disk. But I don't think that's really the issue. It's just a bit more time consuming, and I don't think the band have been interested in doing another one. But I will try to remember to mention it to them if and when they talk about doing another live video release.