How to make purchase orders for suppliers that function like work orders

We purchase many "kits" from suppliers that are order specific. They contain standard parts but we buy standard part numbers, but different part numbers and quantities can be on each order. But we want to track the usage and even forecast the demand of these lower level parts even if we don't buy them direct (sometimes we buy both direct and in a kit. It's basically a work order as it converts parts into an assembly, but records the usage. Also, wereit a work order we would be forecasting the demand or showing the demand where we have firm customer orders.

I have seen this issue over the years but only remeber one MRP system that handled it. How do I do work orders for outside suppliers in JDE?

When you outsource some of the job within a work order processing, Work Order with Outside Operation does create a Purchase Order automatically.

I am doubt for adding all materials used by 3-party to the BOM for Work Order creation, unless you hold the liability of the inventory. You can have this as text on Routing operation.