It seems for me too, there is no good building block to create distributed CP system with Erlang/Elixir, like for example underling Raft-implementation for etcd allows it. Every time I was involved in building any distributed system, it had self-written implementation of Paxos/Raft or some simplified algorithm for own needs. (riak_ensemble is no except, because it is used only in riak as I know).
Just to note, for example etcd/raft is an building block for such applications ( for example raft of etcd is used by many more applications: https://github.com/coreos/etcd/tree/master/raft#notable-users, because of a good architecture of a library, which really allows easily embed and customise to own needs). There doesn’t exists such thing in Erlang/Elixir ecosystem at the moment, which can allow easily build systems with CP properties.
Probably rabbitmq/ra could become something like etcd/raft in Go for Erlang/Elixir. I really hope, that may be something like rabbitmq/ra could become defacto standard raft implementation for Erlang/Elixir ecosystem, which is battle-tested and usable to build software on top of it.
Than, building something like etcd to use directly inside of VM will become very easy task.
