It would be very helpful for integrating other data sources into RE if Import had a way to upgrade existing non-constituent "records" to constituents. As it is, this is only possible manually one at a time, so for the purposes of any large-scale integration, not possible at all.

Also, NXT's duplicate identification tool doesn't look at non-constituent records to tell you there might be duplicates, so if you create a constit record as part of such an integration, there is no realistic hope for figuring out that the same person exists already as a non-constituent record (on an individual relationship, for example).