Hi Reco,
I wrote the guide for OdroidHC1, happy to answer any questions.
To share some background: initially I was looking into a custom sdcard image build by debian.
I remember finding some, but no one could tell me I could extend that list of automatic generated images.
Also the blobs required to boot the device are not part of debian, not even available in non-free. I reached out to hardkernel and asked them formally to add a license for the signed files, as that would be a requirement for distributions like debian to be able to ship them (in non-free at least). But that didn't end up nowhere.
The debian installer sounds great in theory, but in practice you install from one medium to a second medium. But with the device I have there is just a single medium: the sdcard I enter. The disk or ssd can be added optionally, or you can add a usb stick, but neither can boot without a sdcard having a boot loader already. So I'm not sure a D-I installer image would be that helpful. But then, having two options available doesn't hurt.
Regards, Andreas