The quickest way to a major is military experience. The next quickest way is a regional pilot. Sure, other options are possible but rare, don't gamble this opportunity away.

This. I was instrumental in making several changes at the place I CFIed. You can let people run all over you or you can put your foot down. Turns out you can earn a pretty good living doing that with lots of opportunities to fly different aircraft and paths to solid careers. Unfortunately the SJS keeps trying to undercut everything though and there's little reason for any operation to treat employees as if they are a scare resource. Point though is you really can make a change, it takes imagination and determination. It's not necessarily easy, but it's possible. Thinking about how many people got into this job so they could have 15 days off a month and earn executive salaries by flying an airplane, it may be probable that there is little motivation to fix anything...

I don't think anyone would consider being a career CFI. I know I was done with it when I hit 1,000 hours dual given. With the new ATP rule though, a CFI might have other options than the regionals. As far as prospects and job security, just ask the 8 year Comair F.O.s who got kicked to the street and start at the bottom of the regional pile all over again. There are risks either way I guess.
Military is appealing to the majors, but not a fast way to build time.

The hurt has just started!

Below the $32,000 a year CFI gig, there was a king air captain position, air ambulance for $72,000 a year plus benefits. How about instructing year 1 for $32,000, Amflight year 2 for similar pay, weekends off, turbine PIC and CASS, take the King Air gig for a couple of years STARTING pay $72,000 with 7 days on, 7 off, then apply to the majors. Compare that to a typical first 5 years at a regional.
ATP flight school don't advertise this option on their web site though do they?

Probably because single pilot King Air Capts aren't nearly as competitive for majors as regional FOs. Not saying they can't and your scenario is impossible, but it's not probable. Your hypothetical AmFlight pilot would be much better off going somewhere like USA Jet where he can get some jet time on a DC-9. That kind of experience will set him apart for the crowd far more than some Air Ambo gig will. You should also consider that some Ambo gigs only fly 200 hours a year.

I'm not trying to undermine your post but I have spoken with pilots who have tried to do just that and ended up eventually succumbing to the regionals. Like others have said I'm sure its been done before but it doesn't seem very common or most would probably be exploring that route. I would rather go ahead and try to get an interview with a regional with the hopes of having more time off and the option to commute if absolutely necessary. I've worked like a dog instructing and would rather not have to do it for 20 years to maybe skip the regionals.

As far as CFIing goes, I've been doing it for 3 years and have 2000 hours and am 2 hours shy of ATP xc mins. It's a good vehicle to get to where you need to be and save some coin along the way if you're doing it right. Besides the school where I got most of my ratings, I have run across very few career instructors. Most of them are free lance if I had to guess.

I used to complain about the regionals and the dismal pay but the reality is once you get past the first couple of years the pay seems to be decent.

I flew a King Air before taking a job at a Regional. Part 135/91 does not prepare you for a Part 121 airline job, and the majors know it. I tried to skip the regionals, and was told by a recruiter at a major "While your résumé is good, I can't possibly hire you when there are so many qualified applicants with 121 experience."

If you found the only air ambulance job willing to hire you with less than 4,000 hours I suggest you take it, but the fact that you're comparing an air ambulance job to entry-level turbine jobs like regional airlines and Ameriflight demonstrates a lack of understanding of how this industry works.

Is the Regional life that much better than CFIing?

or is regional only better because it's a necessary path to major?