Hi jenn and thanks for using Justanswer.com
The best plan for your daughter will be whatever plan you and your ex can agree upon. Studies have shown that when a child is this young the two most important factors in having her adjust to your divorce in a healthy way are: consisitency of contact with both parents and her perception of your ability to get along well with each other.
It doesnt matter where your daughter spends the night or who picks her up, the constancy that you are striving for, is that she has access to both parents and that she feels you two are both getting along well.
I see that you are looking out for your daughter and as a teacher you are looking for structure and some degree of constancy, and you are right to do so. The biggest factors in healthy development have less to do with the details of the custody and much more to do with the behaviors of the parents and their flexibility.
I understand your concern on this and my recommendation is that you try it your ex's way for a few weeks and see how it goes?
I think she will be fine, but if not you can always renogitiate this plan. Kids are much more resilient and flexible than we are.
I wish you all my very best on this during such a rough time. If you have more questions do ask.