The exclude ability was removed when I rejiggered the xml. The reason is kind of complicated, but essentially in order to build the new variant, it builds from the bottom up. So it has already added the stuff by the time it gets told to exclude it, and in order to do that we'd have to have a new feature that goes back and actively removes those systems.
As a general xml feature, it just didn't work. Overall there are some ways around this, for systems in particular, like on your variant setting the stuff you don't want to not activate until mark 8, or similar. That's a bit crude, but it works for now.