Wait hold on, can you not simply just access the underlying volume/block device using an API? The VMs in OCI have a boot volume that is attached, so I reckon it's possible to "mount" this somehow and overwrite it with whatever data you want.

I am not sure. Maybe it's a thing about not being able to download the iso (no network on the console?) or not having space for it or something. I wouldn't know about the API thing. I am not a cloud user.

Made me think though.