Expanding Master File Options - Not sure what the questions is here. In v4.4, throw the flag in the CI Items set up and 15 character item # becomes 30. You have to rearrange your SO and PO forms but not a big deal. There is a warning that there is no returning to 15. Is this what you mean?
Regarding the Vendor Name, add a udf to the vendor master for the expanded name. Write a script that when you enter information into the expanded field that the first 30 characters are copied over to the name field. Add the UDF to the Check printing form and any other report they want to display it in. Only way to do it currently. I wouldn't go down the DFDM route of the data dictionaries. Way too risky for this one off situation.
BTW, aren't they promising some sort of invoice expansion in v5.0 (v2013?). I don't see the inv # ever changing as long as they have JC and WO still kicking around.