We sell phone accessories, so lets say Item A has 3 child skus. One is compatible with iPhone X. One is compatible with iPhone XR and one is compatible with iPhone Xs Max
Then lets say suppliers say they're updating the mould for the iPhone X one to make it cross compatible with iPhone X as well as iPhone XR.
In this scenario, we would order stock for the new mould under the existing iPhone X SKU, and we would sell out the existing iPhone XR units, and then link the iPhone XR Skus as a composite to the iPhone X sku
However currently when this situation arises, we have to periodically check the stock of iPhone XR, making sure only to link it over once its sold out
So essentially there should be a functionality to state once item B has sold out, then link it as a composite to Item A