You can use open order and delivery request: GESPOC & GESPOD

While this does provide visibility to MRP of intended receipts, it also requires user input to maintain each PO/Transfer. Ideally a forecast type situation is better because it is consumed by time, and requires less user-input.

I agree but we have nothing better. We manage only forecast for consumption not supply. 
Maybe some specific to have some automatic update of the delivery request. Else why not receiving the stock against this delivery request so it will get consumed.