Hi there,
Let's see if I can help you out some with your questions on career goals...
1. Does having straightforward career goals like Management Consulting or Investment Banking sound dull to the adcom? How important is it to craft unique career goals?
Hmmm... I would say the most important thing about your goals is that you can support them.... provide a rationale that makes sense- i.e. WHY are these goals important to you and relevant to you and your career? How will your past career, plus the MBA, support and lead you to those next career goals? Really aim to dig in on those points, in essays and interviews, and if your story seems to make sense and you can explain the 'why' and 'how', then the specific goals become less of the issue or concern. Certainly there are a lot of MC or IB goals out there, which goes both ways-- finance and consulting are still the 2 largest areas MBA grads go into, so that is common and does make sense.... but yes there will be a lot of people saying those things.

Again if it makes sense for YOU (goals can be and should be very personal) then that's fine, if it sounds arbitrarily chosen, then it can come across weaker.
2. How specific do I need to be about my goals? Apart from mentioning intended industry + function + location, is there anything else that is required?
Somewhat touched on above.... specific is good as long as still realistic, and it's ok not to know 100% details, certainly. The overall rationale/explanation of why and how this career path is for you and will work for you is a key component.
3. Although I have a few passions, several career options will allow me to pursue them. Is it possible to say that I am undecided on a post-MBA goal and that I want to use the MBA to deepen my understanding of these career options and then select something later?
While it's possible and ok to say this in theory... in practice, at top ranked schools, you may get edged out by someone who is just as qualified and has a strong case for why and how they'll use the MBA for their career. At less competitive schools that may not be the case as often. Keep in mind schools won't hold you to what you say, but they do want you to be honest/genuine, and it helps to show that you do know WHY you want this degree. So think about it some more and see if there is a particular path you feel would make sense for you. You can probably list 2 alternative options if you are really torn, as long as both seem to make sense, but my advice would be not to leave it completely up in the air.
Good luck, hope that helps!