What you described looks to me like variant configuration, which we use for example for our glass, we produce huge sizes and cut them into pieces according to the customer wish, or just having some left over different from the finished good size which can be used for some future order.
Variant Configuration (LO-VC) - SAP Library
alternative you may think about batch specific unit of measure
Batch-Specific Units of Measure - Batch Management (LO-BM) - SAP Library
and determine which of both is more suitable for your scenario.