Re: How do I un-publish a channel without deleting it?
Since removing a channel is somewhat of a PIA, you should consider posting a new feed file that contains only one video. The video should explain that your channel is "currently under construction". When you have finished your transition, simply update the current feed file with one that points to the new video location.
Windows desktop software for creating and managing MRSS, JSON, and FireTV feeds @ https://github.com/rrirower. No Programming, JSON or MRSS knowledge required.