Here are 3 major update that would really empower the aggregation feature :
When you select multiple columns in preview and click aggregate, it aggregates only one column => it should aggregate all selected columns
When you right click on columns in selection pane, there should be an option to aggregate so that you don’t have to wait for the preview. Now there is only a filter possibility.
auto aggregations (SUM) defined in each connector => for each connector you would have a flag to say that each numeric field would be automatically aggregated by sum.
Big need for us here, the 3rd one is awesome because today users have to aggregate fied by field, and they have to wait for preview. They find it very painful.
Technically it does not seem very complex ?