Congratulations! It's great to see this. I hope to try it soon, and join the polishing effort once I get a bit more time. Other Debian cloud folks may also be interested in collaborating.
Image registration and upload is not critical to have in the script before merging - for the official images we've been building, we've done various rounds of tests before publishing the results, so the process was more complex anyway. It's definitely a desirable feature, but doesn't need to be viewed as a merge blocker.