Amend Batch Number by Location / Split Batches

In the Amend Batch/Serial No feature, you can filter batch numbers by location, but changing the batch number applies to all locations where that batch exists. For example we have item GIN which is in stock at SHOP (qty 100) and WAREHOUSE (qty 100). The batch number for all the stock at both locations is B001. I want to be able to amend the stock at WAREHOUSE to be B002. If I go to Amend Batch/Serial Nos, and apply warehouse filter to WAREHOUSE it will show me B001 qty 100, but if I change the batch number, it applies also to the qty 100 in SHOP. As far as I know, the only way to achieve this currently would be to write off the stock at WAREHOUSE (B001) and add it back into stock as B002 but this is quite a manual process and could lead to differences in stock value unless the user is careful to use the exact same cost price when adding it back into stock. It also requires the user to have write off/add stock permissions in Sage, which is normally restricted. Another way to look at this would be the ability to split a batch, so rather than amending the entire batch, the quantity against any given batch could be increased or reduced, and new batches added, as long as the overall quantity within the bin location is unchanged. Would also be interested to know how anyone else who deals with batched stock currently handles this situation.