I think you may be neglecting to emphasize the importance of how to choose people to include in a custom list. For example:
1. People you've traded with are not necessarily good candidates. You have to trust person's judgement as well.
2. Review the feedback sent by people you're including/excluding. (You've mentioned this a little bit)
2. Never include people who ask to be included. Perhaps exclude them instead. Be skeptical about inclusions suggested by other users (possible shilling).
3. Don't include people merely based on their merits or if you like/agree with their posts.
etc
Including wrong people in the list would negate any advantages and might make it far worse than just leaving the settings at DefaultTrust.
Should this be in B&H?