Is it possible to map doubleclick on folders in Finder List View to Expand/Collapse triangle?
I'm raising my hand…  

 Return ⏎  or  Enter ⌅    is to rename,  Cmd ⌘    O   or double-click is to launch or open.

The Finder is the most beautifully key-commandable environment. Just look at what you can do…

OS X: Keyboard shortcuts (Finder is towards the bottom)

Very simply, in List view  →  &amp;  ←   will open &amp; close the current folder, add the  Option ⌥  key to recursively open/close all folders in that folder simultaneously.
 Cmd ⌘    [   or   ]  will go to the previous or next folder...