There have been a few good hints about changing the menu shortcut keys in Carbon apps by using a hex editor on the Localized.rsrc file. What about the Cocoa apps? I couldn't find a hint here about it, but it's ridiculously easy.
First, make sure you have the Developers Tools installed. Start the application "Interface Builder" located in /Developer/Applications.
Right click on the application you wish to modify and select "Show Package Contents." Navigate to Contents -> Resources -> English.lproj. You may wish to make a backup of the application first, just in case...
Drag the file "MainMenu.nib" to the Interface Builder icon on the dock to open it. You will see the menu bar of your application presented for editing. Just double-click on the various elements to change them. You can double-click on the hotkey letter to change it to something else. Save it and restart your application to enjoy the new shortcuts.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020719085452648