After the DB table transportation it is still needed to execute SE14 to adjust it again in Production box.

No, it is not required  because automatic table conversion process always triggered by the import of the transport request. Only in some cases where automatic conversion process fails due to technical error or because of non-convertible data(for example Text in fields converted from char to numeric ) or If you changed the Key Fields, and you had to adjust table in SE14 in DEV, then  you have to repeat the task in Production also.