I don't see the distinction between an activity and a resource, because, at least for me, the resources are the activities.
This part of moodle is setup based on the technology, not based on how teachers use the technology.
This is how I would set things up.
1. Adding local text
A. Save text as outline (each line of the text becomes a separate "label" item.
B. Save as one label.
2. Creating the lesson.
A. Create local lesson.
B. Create lesson as a label. (in the code, it works the same way as 1B above)
C. Link to external lesson. (The icon indicates this is not only a url, but specifically a lesson url).
D. Link to an attachment lesson.
E. Read an external book, magazine, etc. (required reading).
3. Extra reading (if you want to learn more about this topic)
A. Addition lesson (just a standard Lesson)
B. Attachment (stored locally)
C. Reading an offline book, book, magazine, newspaper.
D. Visit someplace, do a field trip.
E. Reading an online website, encyclopedia, news site, etc.
4. Activities that are not tied to a specific topic
C. File Repository
D. Image Repository
E. Url repository
F. Bibliogrphy (list of offline resources that were used to create the lesson or teacher recommends for further reading)
H. Quiz bank (practice questions for review) -- teacher would need ability to mark which questions to include.
5. Quizzes and Tests
1. Convert single document to quizzes.
2. Create questions
3. Create a quiz/test.
6. Homework / practice
A. From quiz bank.
B. From lesson.
C. URL to online worksheet or other activity.
D. Offline activity (a book, magazine, newspaper, journal, textbook, workbook, etc.)
A bunch of these are repeated activities. The difference is that some of the information is pre-filled and the icon may be different. A url that is intended to be a resource (extra reading) is different than the url that is intended to be the actual lesson (required "reading"). Is the url required or is the url optional?
I think that boils down to how a teacher is using Moodle. Is the course truly a 100% unique full course where all of the material is created by the teacher (owner of the website)? Is it supplemental material with the teacher using traditional lessons and textbooks? Or is it a mixture of the two where the items can either be online items or traditional books and learning resources?