Purchase invoice after Production Order

Hi there, I have some different sort of business invoicing method explained below. I have searched it in forum couldn’t get, kindly guide.

Our business is to purchase tiles and then pack it according to costumer requirements and sale them accordingly, Basically we have two type of inventory (Packing material and Tiles).
For this First we make purchase quotation then receive them through GRN, then through production order we in combine make Tile and packing material one finished pallet. And then sale pallets.
In packing material we make purchase invoice till GRN before production order.
In Tiles, we make purchase invoice after production order at time of sale of finish good and make payment to vendor at time of receipt of sales invoice. Reason of doing this is, we only pay vendor for item what we sale. Finished item not sold is used by tile vendor (no return of payment, as it haven’t done so as not make payable)

Now problem is without making purchase invoice for tiles, Manager software make production order but its finished item quantity didn’t show within inventory.
If we make purchase invoice for tiles before production order then our Payables increased by amount of tiles we process in production order didn’t sold (In actual this amount is not our payable as it didnt sell yet)

Yeah, the cost cannot show in inventory because it’s unknown until all parts are purchased.

But for management purposes, even if cost is not known, the quantity could be added to inventory. I will be looking into inventory module very soon. There are quite a few ideas I have to improve the system to handle various edge-cases.