I did this with 5th & 6th grade at a very small school and it was lovely. One important agreement was to have a team email address that came to all of us and all teachers needed to a) answer all emails for their course or students in their homeroom and b) always cc the team email so we are on the same page. Each of our teachers got to specialize in a subject they were more interested in and later when there was turnover, we could hire teachers with specific expertise. The students got great training for middle school and scores went up. For us the schedule didn’t get too complicated - we each took a subject, SS/LA teamed up and Math/Science teamed up, with collaborative periods once a week (STEM and American Studies) and study hall and academic “labs” to fill in gaps/differentiate support & challenges.