In Which I Form an "Opinion"

If your publishing house acquired a debut novelist with radically ambitious marketing ideas (eg: corporate-sponsored book tour; alternate reality game played by fans in real time around the country; basically, any idea that hasn’t yet been proven effective for the book):
1. How likely would you support those efforts?

You pretty much answered your question with "hasn't yet been proven effective".
You must understand that every debut novelist and writer of any sort has a catalog of ideas about what might be done to promote their special book.

Ideas that may indeed be

• original
• daring
• innovative
  

Ideas that are also almost certainly

• based on a fundamental lack of experience in selling books
  
• moderately or massively expensive, in cash and staff involvement

It can be easy to think that the equation should be as simple as "I have ideas, publishers have money". Doesn't your publisher want to invest in your book?

Yes, your publisher does. But not in any way that might prove a complete waste of money, because people get fired over stuff like that.

Why in god's name would they invest in a tactic they have no reason to think would succeed, when they have other tactics they could spend that very same money on (please note: the only money they have to spend on that book) that will quite likely succeed?

2. If you found the ideas sound and would pledge support, what form of support would likely be offered (contacts/mailing lists, media training, money…)?

Ok, so let's assume you've somehow given the publisher a reason to think a particular tactic would succeed (outside of "it would be so cool" or "it totally worked on my neighbors"). What support would be forthcoming would depend entirely on the idea and how sound we'd found it.

3. If you would deny support to any ideas outside of those previously tested and proven (eg: book review copies, press materials, author page on house website), on what would you base this opinion?

On what would I base my opinion about "previously tested and proven" tactics?!

Wait, wait, back up. "Opinion"?!?

All right, maybe I've misunderstood the question. I am taking a deep breath.
I don't feel I can really help you understand marketing decisions any more than to say that we do need a reason to think a marketing tactic or strategy would work. Not a guess, not a theory, not an opinion. The tactics we use don't always work the way we'd hoped, but at least we were basing them on previous experience, facts, studies, and a realistic understanding of how the book business works. If you can bring some or all of those things to the discussion of radical new tactics, we'll listen.