A customer pays some of his suppliers by allowing them to pull direct debits from his account. It seems that this case is not supported by IFS at all (yet). Is this correct?

IFS knows direct debit, but only where the IFS user is the supplier. It makes no sense to include the payment in a payment proposal because that would pay the supplier twice. And it is not possible to import it via a bank statement file because the transaction code 105 which is used by the bank for this purpose is set  to “Direct Cash” in IFS. With the trick described in the comments of  

it seems to be possible to use the code anyway for supplier payments but we still can see that the function is not really supported - for example cash discounts are not automatically calculated and assigned there. 

So do we actually have to wait for a support of supplier direct debits in IFS?