Business Roles: set field value at text data type also allow all other data type fields to use

Today it is only possible to use other text fields in set function if the field is string based. In our case I would copy the sequencenumber (int) in the position field (string) if this is empty as default. The user should be able to change in non-number format like 1.a or 1.1.1 I know this would be possible by javascript, but this more complex and advanced.