Spot on.
IMHO … the essential elements are:
- “is trusted” should be explicitly determined by end users.
- “filters” that operate from “is trusted” should be subscribable and sharable by end users across all apps. 

Using this simple architecture, “filters” may “ingest” any data or metadata from the network to satisfy for ALL of the diversity of “WoT algorithms” that smart people like yourself have designed. 
- use filters for content feeds
- use filters for recommendations 
- use filters to manage the “is trusted” list itself, so a user doesn’t have to. 🤯

What are your essential elements?