API services required to allow attributes of an item to be updated from an external source

Real life scenario: Our primary spec contains a unit_cost attribute which is managed in an upstream system but is something we would like to display on the item as read-only for end users. When an update is done to the cost in the upstream system we wanted to integrate this change into MDM CE so that the item would always show the most up to date cost.
However in order to do that we found that we could not do a simple update on the item and instead would have to perform many api calls to identify first the ID's of the various catalogs and collaboration areas, then check each catalog and collaboration area to see if the item was in there and finally we would have to know the full path of the attribute for that item. Since this attribute is part of a multi level grouping this was not simple as the path could be something like item/supplier#0/country#2/unit_cost on one item but item/supplier#1/country/#0/cost on another for example.
This proved to be an extremely complex process to try and construct with our integration so we had to abandon being able to show this attribute in the application. This affects all end users of the application as at the moment we cannot add any information from an external source to the item. As well as the unit cost attribute mentioned above there were also other areas where the information is provided by an exernal source which we are now unable to include in MDM CE.

To do the workaround mentioned above would impact the administrators of the application and the Middleware.