It's frustrating for sure, which is why I ended up making my Google Apps (old/free version) account just an alias for my Gmail address.
Enabling Google Fi on Cloud: Suddenly Project Fi needs a dashboard to track all of the Fi accounts for the organization. It needs mass canceling and modification tools. It needs a dedicated support group separate from the main Fi support. Not to mention possible uptime guarantees that would likely be needed. It balloons the development significantly with no real benefit to the service itself. Also businesses aren't likely to use it.
Maybe also view this: https://www.youtube.com/watch?v=KwqDlvJyGI8 that's Google's apps team telling people as recently as yesterday how to turn your Gmail account into a business account.
Imagine you're a small business owner, and that's your only email... you're just about to lose a hell of a lot of things you may take for granted.
Also... https://productforums.google.com/forum/#!topic/play/86WVa8b_... that's a lot of people complaining about this. That topic grows daily.
These all can use Google Apps accounts since I use all of these and I use a Google Apps account exclusively.
I know that's not what you were saying, just curious if that part works for you.
Which makes the list:
* Allo
* Google Fi
* Google Play Music Family Plan
* Google Play Store Family Sharing
* Google Spaces
* Google Trips
* YouTube Red
* YouTube Music
It's a growing list.
I'm always amused by the "One account. All of Google" header on the login pages. Google Apps accounts do not grant access to all of Google as the products do not work for it (it's not a permissions thing the domain admin can fix).