Auto Pick to select batch from 'Related Order' not FIFO

Please look at this issue of Dear wanting to always grab the oldest batch, as when we’ve generated a reorder backorder to fulfil the sales order, we want to use the batch assigned to the SKUs from that purchase order. And I would have expected that Dear already function this way when costing method is 'Batch - Special'. However, regardless of costing method selected for the SKU, Dear always Auto Picks based on FIFO. 

This seems to be a bug, as Dear recognizes the scenario of a Backorder generated in order to fill a sales order, via the 'Related Orders' feature, yet there's a disconnect in the process by not auto picking the batch from that backorder.   

This request could be regarded as an addition, or related to my previous request for: '[proper] Backorder Received Notification', (https://support.dearsystems.com/support/discussions/topics/11000037228) as it would form part of a fully functioning process relating to fulfilling orders once backordered stock is received in. 

Thanks for considering.

Cam.