If I were going to be applying Celsius or any other Sulfonylurea herbicide to an off label or less than susceptible weed, I would be making the tank mix with MSO. Reason why is that I am more likely to get a substantial kill with that vs a NIS.
When I apply Prodiamine, it is normally by itself or with something I need to water in right away. I am not comfortable leaving preemergents not watered into the soil. Now for your program, the Prodiamine would be by itself and then watered in. Now for the Simazine and Monument, that calls for MSO. Simazine and Atrazine becomes a postemergent when applied with oil. Again, this is how it is used in corn fields. When Simazine was legal for use in Hawaii on lawns, I would apply it with either COC or MSO to emerged weeds to kill them during grow in from plugs or sprigs. For your usage, that and Monument would become an effective application against Poa annua and emerged broadleaf weeds.
Do you use Speedzone? I do. If Speedzone becomes part of the application, I skip adding MSO to the mix. Speedzone is formulated with COC. That is part of why it works so well. A lot is being added to the mix as well. If I were to apply 2,4-D ester to a lawn, I only need 1/2 oz per 1000 sq ft, Dicamba as Banvel, only a 1/2 teaspoon, Carfentrazone, as Quicksilver, 1 ML or else 1/5th of a teaspoon. That leaves about 1/2 oz of volume for COC. I only use Speedzone from November til May. After that, I need to think about vaporization of the 2.,4-D and damage to the lawn.