purchase_delivery_address

This module adds a delivery address to the purchase order, which is
automatically propagated to the generated picking.

Moreover, when a sale order generates a purchase in drop shipping mode, the
generated purchase has the delivery address set.

The idea is that this way dropshipping pickings have a trace of the desired
delivery address. The partner_id field of the picking is already used for the
supplier.
and then again... there are a number of cases in the official addons where such things are handled with an xmlid lookup + a search as a backup in case the xmlid was not found.