My own list:
1) Ditch spring-loaded folders in favor of PopupFolder functionality (when you drag a file onto a volume or folder it should pop out a menu showing all contents with the folders behaving like a hierarchical menu; drag onto one of them and its contents pops up and so on. Release and in drops the file).
2) Apple should buy DefaultFolder from St. Clair Software and extend it somewhat, to fix the crippled Open/Save/Save As dialog boxes. You should be able to delete, move, rename, get file type & creator code, finder label, finder comments, and previews of any file in the current folder; Command-clicking the foldername should not only let you slide up the hierarchy, you should also get a popup to the side showing the full contents of any folder in the hierarchy, and be able thereby to navigate not only up-hierarchy but to the side and back down a different path in a single click.
3) Return optional legacy AppleTalk networking. The real deal, backwards-compatible to System 6. And fix SMB, get it faster, get it to quit depositing Finderturds (._DS_Store, etc) inside PC volumes unless they can be made invisible to the PC OS. And include optional legacy PC networking (NetBEUI, pre-Active Directory NetBIOS, etc).
4) Give the option of "placing" the Dock in the main menubar as a Dock menu item (a hierarchical menu of course). Also the option of not only hiding the Dock but turning off auto-reveal on mouseover (so you have to specifically invoke the Dock to make it appear). And put a PrefsPane field to change keystroke ⌘-Tab to something else if desired, or disable it altogether.
5) A "Get Info" tab that's useful. Display permissions in all formats (rwxrwxrwx, 777, "you can read", etc), display size, creator code, type code, file-specific binding, finder comment, label, created & modified dates, "will open with", unix path, Mac path, lock flag, custom icon flag, and any other metadata associated with the file.
6) Fix the Finder window-refresh problem.
7) With the exception of column view, each folder should have a position and a native view; whenever opened, it should manifest itself at that size, shape, and view.