Good to hear from you. Let's hit those questions one by one.
Do I need to convey my much loftier long term goals, or should I focus on my performance to date resulting in the opportunity to be fast-tracked with my current employer (I worry this is too mainstream)?
You should. Absolutely. And your job is not only to dream high, but to build the story leading into it to make these very lofty goals seem reachable for you. Most schools will explicitly ask for your long and short term goals, and actually being fast-tracked in the short-time is a pretty darn good way to make it to the top. And schools know that. If you can get that company support, that would be just another argument in your favor.
If I should convey my more ambitious long term goals, then should I stay away from committing to returning to my current employer and communicate my immediate post-career goal more generically (I'm not sure how communicating an intent to return, but also an intent to leave would be received)?
Not at all! Having a guaranteed managerial position at a good employer is essentially the best thing you can offer a business school, as you will be playing directly into their interests (by having a job, getting a good salary, etc).
And would the answer to these questions differ by school, since I know some schools (H/S) are more demanding in terms of game-changing ambitions than others (I'm targeting top 10-15 schools)?
Not really. All schools like the ambitious and successful (go figure... ) Stanford though, does seem to be just as concerned about the "big picture" beyond your goals... they are always asking not just WHAT, but also WHY and HOW... so think about that as you prepare your essays,
Hope this helps!
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