For the past thirty years, the MacArthur Foundation has awarded "genius grants" to creative achievers to support their pursuit of new ideas. With virtually no restrictions on the money and no obligations required of the recipient, the awards are a vote of confidence in what the recipient is capable of achieving, given the luxury of time. Next time you want a talented employee to pursue a new idea, give out a genius grant of your own.
It doesn't need to be money; you can give slack time so that your star has breathing room to explore her idea. Giving these awards not only will result in useful new ideas, but will signal to your people that you value creativity and are willing to invest time and resources in cultivating it.