Hmm. you DO have a tough and unusual profile. Basically all the numbers seem good, but the career history is a bit wacky. Really, your key to make a convincing argument with those goals is to show how you got involved in MORE than just accounting in Healthcare. If you were just hacking away at the audits at NIH it's gonna be tough to go with those goals. If you have done more, then it's awesome but you are gonna have to milk that cow to the very last drop!
I do like your extra currics in healthcare. They show a dedication and that you have done SOMETHING concrete already to make that jump and that you aren't just "magically" waiting for the MBA to help you do that.
Calling Stanford impossible is what I call "honest self evaluation". Given your background and age, it's gonna be a heck of a long shot. At the other schools you have a fighting chance. You can also look into Duke, Kellogg and UNC which for various and sundry reasons are all good for healthcare folks like yourself.
The second key (which is hard to see from this point) is to make yourself SHINE. You gotta give them more than "I'm an auditor" but even when you are doing audit work, that you have always given your most and gotten the most in return. That, and building yourself a logical career arc with your goals at the end are the two most important things for you to get those accepts.
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