You're making some assumptions. For example if you use epaxos for the quorums there is no unavailability due to a leader failure and re-election. Even then, re-election is likely going to be a lot faster than any sort of fault tolerant 2PC coordinator recovery protocol. You're exaggerating the write amplification. The above offering is single region. Google says they do 5 way geo in their various papers/etc, and there's no way they're paying some cumulative 15 copy write amplification as you imply.