I'm going to commit the above change this week if nobody complains.
Go for it.
I would leave the build.log where it is for now. I don't see a major reason to mess with it.
Creating the tests.log is a good approach.
That's committed in trunk r69559
It will work as expected once jboss-test is released and included in AS thirdparty libs.
For now, new bits do nothing more than generating tests.log