Interesting analysis, but I think that economic conditions and demographics changes things a bit. I agree with the OP that the GOP path to victory starts with holding the McCain states then grabbing IN, NC, OH & FL. But this would only be possible if we assume that the economy is actually a bit worse than it is today. As for the 'final four' states I agree that NV and IA are in the list, but if you look at polling over the last few months then CO and NM are safer for the dems than PA and VA, especially NM which seems almost out of reach. PA seems especially vulnerable due to the economy.
So the 'final battleground' scenario (again assuming worsening economic conditions but not a double-dip recession), would look like this:
GOP candidate: 253
Obama: 240
