Installment Billing within Distribution

[Devo]

I have a situation where a client is entering in sales orders then manually billing the customer through the A/R system at intervals based on completion of the product. Lets say at 25%, 50% 75% and 100% complete. They are booking the payments to AR and Deferred Revenue. When the order is complete, they generate an invoice for Zero Dollars (sales order is entered in that way) and run sales update to get the COGS and INV entries. They then make manual JE to move the dollars from Deferred Revenue to Revenue.

Is there an easier way to do this within the Distribution module or outside of it with Service Billing? Contract Billing? or Job Cost?

Thanks,