I think the offensive play calling will be a collaborative effort. First of all, Macdonald was quick to point out that the job titles for all of his coaching staff do not entirely describe their individual responsibilities. Further, Fleury intends to work from the sidelines instead of up in the booth and that can't be done unless there is a trusted, competent set of eyes upstairs. Finally, Macdonald repeatedly emphasized Fleury's surrounding support structure which can lead us to a couple of conclusions: 1) The offensive support staff will collectively ensure fewer deviations from Macdonald's desired offensive identity and will further reinforce the current week's offensive preparation plan, so that Fleury will be less likely to go off of the predesignated path. 2) The support staff will inherently spawn dialog or otherwise create some form of a consensus if there actually are adjustments or deviations required from the current offensive game plan or offensive focus. Macdonald is balancing between giving Fleury some limited freedom to exert his own vision, but also imposing guardrails to prevent Fleury from going too far away from the team identity like Grubb did. This is how I interpret Macdonald's term, "support structure."
It seems like Macdonald learns and corrects from every mistake he has made, and he has apparently learned a lot from the Grubb experience. He will never allow the offensive identity to stray away from his vision again.