After further discussions with David, I think we should fix the issue. Sorry for any confusion i have caused..
What was not clear (to me at least) at our previous discussion was that it's not possible to create a GUI for the default case with the current design.
1) The reason we have two events (Java Errors and Java Exceptions) is because we can't have exception on by default because of pathological cases, i.e. a loop where Long.parse() throw NFE all the time filling up the buffers
2) So if we emit "Java Error" we want to display it in Mission Control, othervise the event would be meaningless.
3) Mission Control can't aggregate exception and errors in the same table since some exception would occur twice, so they must make two tables; "Errors" and "Exceptions".
4) Now if we turn off Error in "All Exceptions" selection the Error table would be empty, which makes no sense to user.
Being able to see Error Exceptions is important when analyzing a flight recording, i.e if a StackOverflowError has occured or not, so a change to the jfc-file is needed. It's a small fix, only a few lines of XML. Low risk. Fix ready.