You could use a bill of materials for the product that is used purely as a "baseline", allowing for "flexible consumption" where you can change the actual consumed components (material) during manufacture. Or since V17 you can now even manufacture without a BOM and create one afterwards from the components used.

Product BOM example:
1 x Stainless Steel 304 Sheet (grams)

On your work order or manufacturing order, you can specify additional components consumed (raw material) or use the scrap button to dispose of wasted components AFTER first carrying out the nesting calculations (using dedicated software) - Open source Deepnest - open source nesting software is one option.

1. Run nesting to get recommended materials needed
2. Create the Manufacturing Order in Odoo and specify the components required (raw materials calculated)
3. Generate work orders or complete MO and register consumed materials

In this case, you would still need a unique product record with a reference number (SKU) to identify what you've manufactured.

I'm not sure if this is the right answer but it is an approach.

Each nest is associated our internal nest number, eg NEST-12345.  Its our reference outside of Odoo.

In Odoo i have setup a bill of materials for a product called NEST-12345, i add the sheet metal as the component.  With by-products enabled i have then added the produced items as by-products and given them an applicable share of the cost.

Then i created a manufacturing order for NEST-12345 , planned the order, started it and finally completed it.  The stock levels for the by-products are increased, the sheet metal is decreased, and NEST-12345 becomes 1.

I need to check the product costing side of this but the BOM analysis shows the desired costs.

Update: costing seems fine, however i have now realised the next operation is different for each item cut from the material.