Reimage/Ghost from USB flash drive [iso]

Hello-

I have a very unique question. I am in the large format printer service industry. Large format printers are the big Engineering/Architecture printers/copiers used for making big prints. These printers have a small embedded PC inside them usually running a stripped down version of Embedded XP running the software common to only these printers. We are constantly having to update these 'controllers' to newer updated versions. Depending on what version they are currently on usually a patch supplied by the manufacture can be run. But when we are going from one version to the next highest [aka: 6.5 to 7.1] then we have to pull the controller, put it on a bench, connect a monitor/mouse/keyboard. Go into the bios, make it boot to what ever drive type we have, which that alone is becoming an issue since these controllers are sometimes different. Some have no IDE, some do, some have SATA some don't. It seems they use whatever motherboard was on sale that week. Also this is an issue too since the factory Ghost images were once imaged on CD's now they are DVD's and we had to buy all new drives. But the controllers all always have USB. All these printers do have a touch screen monitor that will make navigating to BIOS with a USB keyboard easy. So I know it's possible to boot an image from a USB flash drive containing an iso image. Having to remove the controller to enable the "boot from IDE/SATA Optical drive" and connecting that drive is a time consuming process. Yes, technically we could have USB optical drives, but what I am looking for is a portable faster method here. Does this mean we have to have that iso image and only that on one flash drive at a time? Can we say have a larger portable USB (disk/plater style) HDD and have it partitioned for different update versions?

I should also add, that before doing these updates we do have to backup important files, so being able to back them up to the same USB drive holding the iso ghost image would be beneficial.

Any help would be appreciated.

Thanks!