How about a file that can be downloaded for codex/forum users who are having trouble finding their own problems. Instead of asking a user to create, upload, and view various files with stuff such as phpinfo(), we create a file that they upload, and the file can help them diagnose problems for a variety of situations. Here's a few examples:

• When information is needed from phpinfo();
• Checking file permissions (and auto-adjusting them to what's needed if possible)
• A possible header errors fixer script, where they can paste the error and the file will (if possible) change permissions on the file, edit it, write it, and change permissions back
• Blank files, files that didn't finish uploading, missing files
• Outdated version (do this automatically on every page load, since most people wouldn't even think about it) and maybe even attempt to update the files (borrowing code if possible, if not maybe leave this bit alone
• Unload plugins that may be causing breakage
• Check for IIS and tell them its a terrible idea (joke, but it really is a bad idea)
• A way to rollback to where before the changes were (maybe borrow some code from a backup tool)
• A full options editor as a replacement for phpmyadmin
• Password fix tool for those who have forgotten their password (will insert the new hashes required)
• --more as I think about it

It will display a list of possible fixes that they can click on and guide them through attemping to fix their problems, and optional edits that make it require a password and/or IP address for security