I'm not sure where your getting the idea that people don't modify the bios rom that comes directly from the OEM. People like to post backup's of their bios that were created by tools like "Universal BIOS Backup Toolkit", but we usual just ignore that and ask for a link to the official update. The guy who made that utility says that he can't gaunrentee that it'll work perfectly for every chip, so I personally don't trust backups generated by it
I wrote some tutorials a few months ago on
my blog about modding Insyde bios. However some of the stuff in there is outdated now. Going to start rewriting a lot of my tutorials on this site soon, and I'm going to make them a whol lot better