Hi,
In addition to cash position report, you would then look to liquidity forecast report to reflect the open items in account receivable/account payable subledger from medium-term liquidity perspective. Liquidity forecast report also can integrate itself with SD open sales order as well as MM open PR/PO also.
The key component in Liquidity forecast is Cash Planning group, which is a field in Vendor/Customer master data at company code level. In terms of designing the planning group, you could implement the design of cash planning group as payment method for the customer/vendors. You will need to define the cash management grouping to define how to structure the report FF7A/FF7B.
For liquidity forecast report, the key date is "Cash planning date', a bit similar to due date, however, this date appears to take into account the early settlement cash discount, as well, so can be different from due date.
Hope that this helps you a bit.
cheers
taro