I don't believe it has... do you have access to Report Builder? I believe that you can use custom metrics there...
One thing to note.. when using Data Warehouse and Report Builder... the content that comes out is rendered to the dimension that it's paired with... by which I mean that metrics such as Occurrences and Page Views (metrics that can be added together easily) are fine.. but other metrics such as Visits and Unique Visitors (metrics that can be set on each dimension, but the total needs to be compensated to de-duplicate the total) are tricky
So you might have PV/UVs for item 1 and item 2, etc, but you cannot add those two (or more) items together to get the PV/UVs for the aggregation of the data set.