Decided that since there's not a big advantage in having many collections over just 1 collection to optimize for 1 (or fewer collections) and go with the cleaner model of having taxonomies defined in collections. Can always build in sync support of taxonomies later if not being able to reuse them across collections becomes a big issue.
Decided schema can be defined at collection, taxonomy and category level. Attributes defined at the collection level apply to all items in the collection. Attributes defined at the taxonomy level apply to all items categorized in that taxonomy, and attributes defined at the category level apply to all items categorized at that category or below.
Improved docs about the various types of slugs.
Began to work out the JSON format for taxonomies.