You're really not considering the potential employee here. When interviewing for a job, unless the company is very well known, a Google or a Microsoft, a candidate will probably know relatively little of your company, and probably have no understanding of your mission. How can you expect them to be driven by your mission if they don't know what it is?

You could say the best way for them to find this out is by doing this 3 week contract for hire idea, but that's still a risk to the candidate.