I don't know if I can call this a bug, for it seems it's done intentionally; however, here it is:
I told WeiDU to copy a 25 mb file to the override folder, and I had this message displayed:
"ERROR: [ImoenRom\extra\AR26MR.tis] has size 24576024: TOO BIG FOR WEIDU
So files WeiDU can handle are limited to that size... is this a bug, or simply it's something that WeiDU can't do?