It's not clear to me why this was made. We'll ignore the question of why you would want an ISO (you can write a DMG direct to USB, and Jamf, DeployStudio, etc,

It's not clear to me why this was made. We'll ignore the question of why you would want an ISO (you can write a DMG direct to USB, and Jamf, DeployStudio, etc, require a PKG...), and move on to optimization. You can skip a lot of the convert/copy/asr steps by just using the hdiutil -srcfolder command, targeted to the createinstallmedia DMG, in conjunction with your target format. (This can be reproduced in Disk Utility as well, by the way.) As far as I can tell, you need about 3 commands here, and not a 189 line bash program with functions. As mentioned elsewhere, Disk Maker X is the way to go. Thanks for sharing your work though, even if it's a bit over-built.