I think you are basically right. Blooomberg’s availablity further erodes Rudy’s electability argument and enhances Fred Thompson’s electability. If Bloomberg does run, he will take 3 votes from Hillary for every one he takes from Thompson. He will not threaten Fred in any Red States but, if he catches on, he will destroy Hillary in Pennsylvania, Florida, New Jersey and probably a half dozen other blue states that she cannot afford to lose.
If Rudy were the nominee, Bloomberg (along with an inevitable social conservative third party candidate) would sink him for sure
That said, Bloomberg is a very unappealing candidate who will likely have little impact.
Don’t even think about PA: it will disappoint you every time.
He may spend $1 billion on the race. If so, he will have impact. The billion dollars is his words.