DR,
My intention in answering your post was to help reduce your confusion about the choice between strategies 10 and 40. My intention was not to design your solution for you.
One way to prevent MRP from considering stock is to move the stock in question into a storage location that is not planned. Another way is to change the category from 'unrestricted' to 'blocked'. There are others....
You can run MRP according to whatever schedule that meets your client's requirements (on the first, or the 25th, or on any other days that meets your fancy). You can exclude or include whatever you wish during any of these runs. I am not going to remark on the lunacy of making selected stocks not relevant for planning between the 25th and the end of the month; I am going to assume that you already have intelligently argued your case with the client, and he remains unconvinced. In the end, you have to do whatever he requires.
Best Regards,
DB49