For what it's worth, I was able to add my custom domain to iCloud under this exact scenario without any issues. This was 3 years ago, so I don't know if anythin

For what it's worth, I was able to add my custom domain to iCloud under this exact scenario without any issues. This was 3 years ago, so I don't know if anything has changed, and I didn't have the 'catch all' limitation either.