Not a few education researchers, along with others in psychology and related fields, maintain that we are more efficient and productive when we focus on one task at a time. While there are more tasks for university professors than research and teaching, these are by far the primary functions. Would both research and teaching be improved if a professor could choose to devote full-time to teaching one semester and full-time to research the following semester?
A minor negative impact would be on the department chair scheduling classes. As a former department chair I can confirm that this would be a minor "headache" for me; in fact, I enjoyed working out these "puzzles."
Imagine that you're in your lab or office and you have an epiphany, a brain storm, a brilliant idea or breakthrough right before class. You have to mentally put that on the back burner and try to focus on your teaching. However, during class whether consciously or not, you are using only a portion of your mental faculties on teaching (thereby diminishing your classroom effectiveness) and a portion of your thought processes on your research "bright idea" (again, diminishing effectiveness due to lack of full attention).
Now that I think about it, I recall this happening to me more than once. I would think out word for word a paragraph for an article or book. I'd go to class and was able to focus entirely on teaching (because it was enjoyable, fun, restful, and not nearly as mentally taxing as thinking about "deep" stuff). By the time I got back to my office I'd forgotten most of my "brilliant" paragraph I had mentally written before class, hence, not very efficient or productive.
In short, do you think teaching quality and research productivity/quality would be improved if professors were allowed to choose the alternating research/teaching semester model? Bring it up at your next faculty meeting!