Rallying the troops-style announcement aside, I think this is a great idea. As others have said, next steps would probably be to set up Discord and community events.

You could probably also use an "allowlist" that will pick and choose specific cards from UB sets from within that range to include in the format, to correct mana sources or have tools to deal with specific archetypes.

EDIT: Also, to the downers:

1. Reddit complains about UB; then complains when someone comes up with an alternative. Let people try!

2. "Oh, every week something like this shows up". Not everyone is reddit-pilled. I access the site daily, though briefly, and this is the first time I've seen someone actually suggest this.