So, you are only talking about removing tests that don't work correctly? Not tests that work correctly and fail because the code is buggy.
If we know that a test is improper then we just delete it. We did some of that. If we know how to fix it then we fix it. We did a little of that. Sometimes it is not clear whether a test is correct. Sometimes we know there is a bug but we don't know how to fix it. In both of those cases, we moved the tests to Mantis.
Moving a test out of the image does not mean it has gone forever. A test that fails is a bug, either a test that shows a bug in the code or a buggy test. Bug reports are supposed to be in Mantis. The tests in the image should all work so we can tell that if we run them after we make a change and some of them fail then we made a mistake.
-Ralph