Well, if you do "5" right, "4" isn't so much of an issue
If your pieces are small enough, you should never need to change more than one at a time. Whenever I find a problem that requires changing more than one class at a time to fix, I break something out into a new class, because obviously the functionality wasn't properly isolated. (Modulate this for "fix it now" vs. "fix it right" of course.)
We have to fight the terrorists as if there were no rules and preserve our open society as if there were no terrorists. -- [link|http://www.nytimes.com/2001/04/05/opinion/BIO-FRIEDMAN.html|Thomas Friedman]