Wow, congrats on the new job offer, and definitely sounds like you have a lot to think about!
It sounds like a nice promotion and opportunity, and if I'm understanding correctly you are planning to take it, so I would think it's acceptable to tell the business schools of the promotion/position. For those you've already submitted to, I would start with a brief email inquiry to the admissions office basically saying you just received this new opportunity etc, and asking them if it's appropriate to send notification to the admissions committee... let those fielding admissions emails and questions advise you in case any schools are more strict about information coming in after-the-fact. No matter what, it would potentially come up in any additional interviews and applications you complete.
And for those apps you haven't submitted yet, as well as interviews potentially, yes I'd assess whether the goals you had described still make sense or should be tweaked. You should still be able to make a compelling case as to WHY you need the MBA... if YOU can't, then the admissions committee certainly wouldn't be able to!
And as for unethical, I think you are asking if it would seem unethical to the adcom if you took a new job? I don't think that is a factor, and being in the role for about a year is also better than a few months for example.
Hope that helps, good luck!
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