The ways to draw attention to a question are:
offer a bounty (this is what they're designed for, with one exception1)
publicize the question to people who might be able to answer, e.g. through social media (there are even badges for this)
The voting system is fundamental to Stack Exchange; making it context-dependent like you propose does not seem productive, and I don't see the merit of this specific suggestion. What does voting rep for the asker of the question have to do with the current publicity level of the question? The bounty is already drawing more eyeballs which should draw votes if the question is well-asked.
And yes, bounties cost rep and can be risky; I've had more than one expire without getting an answer. Think of the bounty as buying attention (and potentially an answer), not buying an answer.
1 There is a bounty reason for "this has an answer that merits an additional reward", but even with that one you can't award it right away. The primary function of the bounty is to give extra attention to the question.