I can't say an exact answer for the creation of an ISO as you say in your question but if you wish to reduce the amount of time for creating identical copies of an operating system in different computers, the Cloning process can be useful for your case, of which I suggest you the usage of Clonezilla which can be useful for cloning hard disk drives even for those situations on which you need to do it with different size disks as mentioned here: http://www.tuxradar.com/content/how-clone-hard-drives-clonezilla
Moving to a bigger disk
It's easy to ensure that a clone of a SCSI
disk is restored to a SCSI disk, but you'll have a tough time finding
an exact replica size-wise. The good news is you don't have to restore
a disk on another disk of the same size. The even better news is that
you can in fact restore the image to a much larger disk.
When restoring a disk, Clonezilla enables you to resize the filesystem
and create partitions on the new disk proportionally. But even if you
are moving to a bigger disk, you might prefer to keep the partitions
as they are. In that case you can ask Clonezilla to create the
partition table as its listed in the image.
There is documentation about moving to a larger disk but I am not sure that you can do it the opposite (cloning to a smaller disk). That's why I should suggest you to use just the amount of hard disk drive space needed for the install or check which is the smallest hard disk drive of your equipment in order to create the install based on that disk. Let's say: If you have 9 hard disk drives, 2x100GB, 4x80GB 2x40GB and 1x20GB, let's use the smallest one to install and to be the source for cloning so you can clone it in the largest ones. Remember to expand the partitions as needed in order to use the full hard disk drive after cloning.
Clonezilla offers several Live CD's and bootable USB images and there is also documented that you can resize the free space on the disk after the copy, in which case the suggestion to use gparted is also a good idea.
You don't need to worry about drivers and possible failures related to these things. Ubuntu will install whatever drivers as needed for the new computer, except the proprietary drivers of certain video cards (ATI/nVidia) or more specific hardware. Based on that I suggest you to check every cloned system in order to make sure that everything is running fine after the cloning.
By using a cloning procedure you can do as many customization as you wish to the system and be sure that all the cloned hard disk drives will have the same software that you include on the original.