Veep choices are, quite frankly, not that important. The media tends to overstate the VP choice in order to give them something to talk about during the summer months.
I think the only really important thing that McCain does with his VP pick is that he doesn't choose someone who is a Bushie. McCain has, so far, sufficiently convinced independents that he is not simply an extension of Bush. He needs to make sure he doesn't undue his progress.
That being said, for the exercise in mental masturbation, I'll chime in on Bloomberg:
First off, let me preface this by saying that I find it unlikely Bloomberg would accept the VP slot on McCain's ticket, given his past statements, though it is probable he's not being entirely honest.
Bloomberg would be a bad choice for McCain for a number of reasons:
1.) There is no way he could deliver his home state for McCain.
2.) I don't believe that, even with the Jewish vote, McCain would win CT or NJ either.
3.) Bloomberg would reignite and possibly cause the base's suspicion of McCain's conservative credentials to explode. I'm sure McCain is trying to make them forget about it, and make the other side appear so bad they'll have to turn up their nose and vote for him. Bloomberg would only hurt that cause.
4.) Way too many of Bloomberg's policies aren't in line with McCain's.
5.) McCain's spending is capped at $84 mil, extra money won't make a difference.