Consolidating Installments

Does anyone have any ideas for how to consolidate installments from different invoices for one customer on to a single invoice?  I've looked into Balance Forward Billing, but you can't set up the BFB term with installments.  We have the following scenario.  

Order is fully shipped

Order is invoiced in AR

Invoice has payment terms that creates 12 installments so customer can pay the invoice in 12 equal payments.  

Customer may place multiple orders a month that ship.  Most invoices have multiple (12) installments.  

This gets very confusing to the customer to receive multiple installment invoices each month referring to different sales orders.