We created this role and I am sharing it to see if permissions can be further refined so please let us know if you find anything that shouldn't be.
This new role allows a user to see course materials but not change anything. They also cannot see any student grades etc. Teachers add other teachers to their course with this new Collaboration Role when they want to collaborate and share activities and quizzes. Once you add a user with this role to your course they will see it appear when performing a Course Import.
This is much safer than adding someone with an editing teacher role.
Try it out and let me know if you see any glaring issues. See collaboration.xml file attached here.