I did not find your post before posting on TestStand Idea Exchange, but it is the same issue (Kudo?).
Using a statement, I am able to read a CSV file that uses semi-colon (;) intead of comma (,). If your input stream reference is stored in Locals.MyInputStream:
Locals.MyInputStream.AsCsvFileInputRecordStream.SeparatorChar = ";"
It does not allow to use all the Input Data Stream configuration pane functionnalities (preview for instance), but at run-time, it works.