Can you post the script that you changed (eg, standalone.bat, or standalone.conf.bat), and how you modified standalone.xml? Also please post the actual error message you are receiving when you say that the server wasn't starting after you made the changes.
I looked at the source code for the HttpParser1 class in JBoss Web 7.5, which is what is documented to ship with JBoss EAP 6.42. The class has a static initializer that includes populating an array that indicates whether certain characters are acceptable in the URL. The array itself has a size of 128. In your system property, are you only specifying the characters listed above, or are you including some high ASCII characters as well? If you include anything higher than ASCII 127 ("delete"), you'll get an IndexOutOfBoundsException, which would prevent the class from loading.