You can decide that inventory of A item stay on WIP location because you reuse this item as material in new PO.
Also, you could be open two WIP location for each WC. Then you coul configure:
A->WIP1->Production
A->WIP2->Transfer (from WIP1)
B->WIP2->Production
B->FG-Store->Transfer (from WIP2)
In any case, A item, when it is produced, is still in production process (WIP).