Limited sync is available for the home screen. Settings > Accounts > iCloud > One Home Screen (On). This will ensure apps appear the same on all ATV logged into your iCloud account. Will download new apps, put them in the same location\folder. But, login is still a bit of a buga-boo.
SSO, if your TV provider supports it, will help, but otherwise you still have to login and authorize on each device. I suspect this is more of a provider demand than Apple. Hoping for enhancements in this area in future releases, but for now, something we have to live with.