Mac OS X 10.8.3 is out in the app store now, and it includes support for my 2012 Mac mini, so I'm no longer running a custom build, so I thought I'd try again. I'm now running 10.8.3 build 12D78. I can now download Mac OS X install kit from the app store, so I tried again to update my Mac OS X 10.7 guest VM under vmware fusion 5.0.3 (1040386) with no luck. I also tried creating a new 10.8.3 guest using the install dmg and got the same kind of boot shell errors.
I no longer hold onto any hope of running Max OS X 10.8+ as a guest OS on my mac mini. I have no problems booting up Linux VMs, which is my main area of focus anyway.