It's increadibly easy (although the computer will spend hours crunching) to make a boot disk for pretty much anything using buildroot. That honestly sounds like a better plan for underpowered hardware than expecting a major distro to support it.
This is definately something I need to look into. Not only would I be able to produce install images but also would have the chance to learn more about what goes into making that ISO file I take for granted. Thanks for posting!