https://github.com/MariaDB/mariadb-docker/pull/377 is a community contribution to start a galeracluster automatically. It contains the logical to pick the first wsrep-cluster-address address as the first node for bootstrap.
Is the logical around this and the gvwstate.dat state correct?
Are all the of the constructs around hostname correct?
Are their any obvious configuration settings that would impact the correct bootstrapping of the cluster using this?
Recovery from an entire cluster down scenario will probably come as a separate change.