In the military, there is a document called the Warning Order. It is used to provide troops with a heads up that they are going to be going on a mission in the near future. It gives them enough details so that they know roughly what to expect and can plan accordingly. That said, I do understand that the details of a milsim mission cannot be given out publicly before the game and that often they are tweaked in the days leading up to a game.
That said, I do not see why units cannot be given guidelines of what to expect well in advance. This would allow them to tailor their gear to the type of missions they will be given and to train accordingly. For example if they are going to be setting up a defensive line, they will want to brush up on how to set up interlocking fires and coordinate with other units on where they want to establish hard points and cover defilades.
My proposition is that every unit be issued a Warning Order (WARNO) prior to a large operation. I have put together a sample WARNO as seen below. Those who would rather read it in PDF format can find it here. For smaller events I would like to see a condensed version of the WARNO (1-2 paragraphs) summarizing the types of missions your unit will be expected to handle, their duration and how the game will be scored given out a few weeks before the game.