How to create capacity work load based on historical sales while having MRP messages for firm order

Hello,

We have different type of demand profile : Make to order MTO / Make to stock MTSfor the finished goods that we sell.

For Make to Stock, we use forecasts (BF) based on historical sales and we have defined safety stock. We use MRP for all our items.

For MTS, we produced the highest quantity between the actual orderbook and the forecast and we refill our safety stock.

For MTO, we only produce the quantity for the sales orders we have in our system.

And what we miss to have the most precise possible view on our work load capacity (in our SIOP process as well), is the work load linked to MTO items for whichwe don't have the firm orders yet but we know that might come.