The ability to have predefined built-in function in the field screen to transform the field without having to create an SQL script.
Ex : * Remove Comma * Format a phone Number * Format a date * Make uppercase/lowercase
The complexity here come from the fact that these function that we would define would required to work for any type of source (OData, MySQL, CSV, etc...) so this may not be easy to do or even possible as we got generic connector such as ODBC.
The ability to create a calculated field work just perfectly but required a bit more technical skill and required more work than a pre-define function.