I would like a decelerated option also, in case things with the family need more attention, however I can understand how schools would be hesitant to offer this.
Unfortunately, they do have to think of their revenue. With the limited number of seats available, they are committing one of those to you for that particular class. If for some reason you take time off, you are possibly going to be taking spots from the subsequent class. Also, the entire school budget is based on the tuition/fees that they expect to get from the students. A smaller school may have a fairly tight budget, so the loss of 20-30K+/yr/student may cause budget issues.
I'm not trying to say that it would make you any less prepared to be a doctor, I'm not sure how it would effect boards. Just for the average school to accomodate this would be difficult unless they have a specific pathway set up for this purpose, if they did it would be great, but again most med students are sick of school already and want to get it over with, so I'm not too sure how popular it would be.