Re: Remember your money is important to us, but you information security is worthless.
The problem is that due to the way ARM works, what you want is essentially impossible. There are no standard hardware interfaces, no standard boot chains, no standard security model etc. Hell, on some devices the thing that you would call "the CPU" isn't even the one that's in charge of device operations.
On a PC you can fall back to BIOS/UEFI to get some things done (drawing to the screen, reading mass storage etc) but that just doesn't exist on ARM devices for the most part. Until this is resolved, "universal" images for ARM are a pipedream.