As a follow up to the discussion on the review request at https://reviews.apache.org/r/46803/ I have updated the tier management proposal document to compare the options for implementing the defaulting logic for the tiers.
Please feel free to comment directly in the doc: https://docs.google.com/document/d/1erszT-HsWf1zCIfhbqHlsotHxWUvDyI2xUwNQQQxLgs/edit#heading=h.x1y1n2g8av7i Thanks!
