Will, although just using the donnor car title would appear to be a simple way to proceed, I think there may be problems in many cases. For example, when you go to sell the car it is possible the buyer may not be a deeply knowledgeable enthusiast and would be scared off by a title for an Eclipse or Talon that is clearly no longer an Eclipse or Talon. I would think in many cases the donnor car may actually be a "wreck" with front or rear damage that the insurance company wrote off. In that case you would have a salvage title and the states I am familiar with require an inspection (not unlike the inspection a self assembled vehicle has to go through) in order to get a new title. In this case the inspectors will clearly see that the car is no longer an Eclipse or Talon. Also, you end up with a title that says salvage or rebuilt vehicle, if somehow you can sneak it through inspection.
Are you aware of any issues with the design of the car that would prevent just going the self assembled vehicle route to begin with? I think I personally would prefer that route, although I can see where the simplicity of just using the existing title has a certain appeal. However, when you go to sell the car it might lose some of its luster.
In any case, I do like this car and am looking forward to the day when it is available to see in person. Regards, Bill