sort of like a bounty for existing answers
But ... that's exactly one of the dedicated purposes for bounties:
An additional benefit is that a bounty bumps the question to the homepage, and it gets featured, so you might inspire more users to vote for the answer.
No, Wolfram|Alpha questions should be explicitly off-topic, regardless of whether W|A is being used through the web interface or Wolfram|Alpha Notebook.
Vote here if you agree (and post the opposite answer for voting, with appropriate arguments, if you disagree).
The interface is a minor detail that should not decide whether W|A is off-topic or ...