Batch number may contain multiple qty, then how its possible to track individual one?? (even with Z - report)
Only with material (without equipment), you can created Return order, but I am not confident about warranty details. This is for Equipment only not for Materials.
Without activating, how can you make Equipment?? How you can see in IE02??
To track Maintenance history of your returned product, you have to create Equipment. For that, you have to activate material master with serial number profile.
Either client should follow this process or they have to adjust with high level details till the return order for product. They should not ask for maintenance tracking without Equipment & Serial Number.