I'm not against changing that behavior since it's arguably stupid and inconsistent [1], but I'm wary of "trivial" changes. It's not only apps that need fixing, pretty much every library needs checking (and maybe fixing). This cannot be done with a commandline check, since classnames can be constructed on the fly, called via eval() or call_user_func() etc. Class names may be loaded or even defined on the fly (the SOAP Pear Extension does this to create proxies). All those cases can only be checked by executing the program. It's probably a good change, but this is anything but trivial.

[1] actually, I don't care at all since I moved on to greener pastures.

Like the ones that they introduced to fix array[key_without_quotes] where key_without_quotes was mapped to a string if it was not a defined constant and a NOTICE was issued? The first thing everyone did was turn off E_NOTICE since practically all code emitted that notice. It took years until you could run apps with E_NOTICE turned on :)