In the process of developing a new implementation for the Elasticsearch Rollups functionality we came up with the concept of the aggregate metric field type.
The aggregate_metric_double field type can store the results of aggregations (currently min, max, sum, value_count and avg are supported - more to come).
This field allows us to run (min, max, sum, value_count, avg) aggregations on the container field and the field will return the correct metric depending on the aggregation that is computed.