While, in general, I like to go by the concept that nothing is impossible, the entire architecture of the board was designed around the Atom processor, and would not be easily modded to accept a chip like the Core 2 Duo easily. Asside from the pinouts and other chipsets being effected, the BIOS was designed around the Atom, as was the battery and power supply. That means replacing, not modding the Motherboard, power supply and battery. Finally, the heat generated by a Core2 is different, so you would have to do something with that too. In the end you would end up with something that Frankenstein would look attractive next to.
What we need is a Atom Duo, running at 2ghz. And a Netbook designed around it.