When running a data import it would be incredibly useful to enable the use of Expressions in the Lookup functionality.
The explicit use case is when the data types do not match across databases. Salesforce stores IDs as DT_WSTR, while Pipedrive stores IDs as DT_I4. So with the type mismatch, you have to figure out workarounds to get the IDs to match up. A simple data type cast would solve this in 1 line.