first of all I am no expert in this part at all. What I see is that the elements of the XML-file are defined in the table tfcmg026. If the Element is "010301000000" then the Bank number (bano) is used. If the Element is "010302000000" then IBAN is used!
What you could try is to copy a working layout with IBAN in tfcmg0524m000 and search for and change the element in the new layout in tfcmg026. And use the new Layout for your Oman-Customers etc.
An export would do this with a blink with standard sessions (tfcmg0624m000,..) Somebody like me would have to use ttaad4100