Going through all the ratings in such a short time doesn't allow any "seasoning experience" between the ratings. An FAA certificate is a "license to learn". Much learning comes from "using" the training you get out there in the real world, outside the academy enviornment.
I don't believe it's ideal to go from PPL to CFIME in 90 days, and then start teaching the next guy. ATP has been doing it for years but I just don't agree with the practice.
That said, sometimes ATP is the best option for certain folks. To each his own. Just don't be sold on the program based on the marketing or talking to a recruiter. Slice will suggest Prarie Air Service. White Air, CPS, and Skymates are other options to look in to. If you've really done your homework and think ATP the way to go, then more power to you. But don't discount the downsides and don't discount the lack of experience you'll have to be a competent CFI going from PPL to CFI in 90 days.
There is an ATP forum at
www.jetcareers.com Check it out. Much more info there.