the "have the scan code automatically entered" is ay less trivial than it can sound it would require: 1. to convert the actual barcode to a sequence of ~90 pixels (0=black bar, 1=withe bar) 2. give the user a way to load such a sequence into MAME/MESS
while I think it is ok for an user to type in the menu 8/13 digits for a barcode, I don't think he would like to type such a sequence
we will need to face the problem (e.g. to support the GBA e-cards, which are dumped as sequence of pixels) but we are not there yet