1) Copy QuitSomethingElse App to the System Folder.
2) Copy QuitSomethingElse INIT to your extensions folder.
3) Restart.
4) When the Finder runs out of memory while loading an application, you will be prompted with a dialog allowing you to select multiple apps to quit (not the Finder's default recommendation).
5) You will have to try launching the intended app after quitting the others apps. I could not figure out how to capture the launch information from the Finder.
6) There are some Finder memory prompts I am not intercepting, but those can be easily added to the INIT project.
