> As we know, the crc32s of many roms show up wrong with cmp.

No. They are correct. Your files are wrong since they either have a wrong byteorder or a useless header.

> include a 'ignore crc32' function on the rebuilder?

No, since this doesn't make sense. The rebuilder IS a crc32 compare routine.

Roman Scherzer
ClrMamePro