(I don\'t want to hear about how crazy I am to want that! :)
Focus-follows-mouse is also known as point-to-focus, pointer focus, and (in some implementations) sloppy
Although this is far from a complete solution, two handy actions that are built into OSX (10.11) are:
⌃⌥-click (control-option-click) - switches focus without raising window
⌘-click (command-click) - clicks in window without switching focus
Not sure when these shortcuts were introduced, as I haven't been able to find them written about anywhere.
Unfortunately CodeTek Virtual Desktop Pro is no longer developed, and the company seems to have gone out of business a few years back..
Historic reference: http://www.codetek.com/ctvd/ (does not work on new OS X versions!)
Historic review: http://www.osnews.com/story/6144
Using CodeTek Virtual Desktop Pro you were able to get Focus-Follow-Mouse and disable Auto-Raise, and it also had a Pager for the virtual desktops -- similar to how Fvwm works on Linux. It really worked perfectly -- the best piece of software that I've ever bought. It worked consistently with all apps, and switching apps, moving windows to different workspaces, and navigating workspaces worked much easier than how it is implemented in the latest OS X versions [10.6, 10.7, 10.8]
Unfortunately with Mac OS X 10.5 VirtualDesktop Pro stopped working, and it looks like Apple actively made sure that CodeTek will not continue to work on it.
It is sad that Apple crushed CodeTek and it's product - Virtual Desktop Pro was really superior to how OS X workspaces are currently implemented. It worked basically like Fvwm on LINUX - super fast navigation -- without unnecessary clicks or mouse gestures...
It saddens me to see that Apple dictates window manager (Finder) behavior and does not seem to allow third-party replacements for the Finder anymore.
Interesting that Leopard has one flavor of focus-follows-mouse (sans autoraise) enabled by default. The scroll wheel works in unfocused windows.