As a product manager I would like the ability to set a percentage of users who get sorted into one bucket while all other users get sorted into another.

This would allow us to set a banner test in bucket A and direct 10% of people to that bucket while offering no banners in bucket B. This would be a true, full test of an A/B, banner/no banner test. The 10% of users would get a full campaign experience while the rest never get anything.