You may already know that even if you install a Notes Standard Client (the one with the Eclipse stuff) you can force the start of a Notes Basic Client by creating a new shortcut to notes.exe adding the parameter "-sa".
Now think of a situation where you want to have ONE software installation pack for all your client but make it up to the user to decide if he wants to start the Standard or the Basic Client. You will find out that using a second shortcut is not sufficient as Notes may be fired up by clicking a mailto-link in a browser or use "send to email" in his Windows Explorer.
The trick is that notes.exe does a very simple check which client is installed, it search the program directory for a folder "framework". If it exists, the Eclipse GUI will fire up, if not we will see the Basic Client GUI.
So the trick is to have a small batch file that renames the folder "framework" to eg "framework.disabled" and back on the choice of the user.