it's been talked about often in the past, and everything that has been said here is pretty much the conclusion that's always been made...I don't know who the hell would be willing to spend the money for a proper targa roof on this car, and even if they did, it would look like shit anyway.
For what its worth, there is a guy on the 3SI forums that rebuilt a 3KGT from virtually its frame and incorporated a targa roof in the process. It looks fantastic (I can post pictures if anyone hasn't seen it), but it's also a completely different animal compared to the turd gen Eclipse.