Procedure to replace a BDR server
We use to do the following: 

1- create a new node

2- Copy data from the node that you want to keep

sudo -u postgres \
    /usr/lib/postgresql/9.4/bin/pg_basebackup \
    -h $HOST_TO_CLONE -p 5432 -D $DATADIR


3- Join the cluster: 

sudo -u postgres  /usr/lib/postgresql/9.4/bin/bdr_init_copy \
    -d "host=$HOST_TO_CLONE dbname=$DB_NAME port=5432" \ 
    '--local-dbname="host=$LOCAL_IP dbname=$DB_NAME port=5432" \ 
    -n $LOCAL_IP -D $DATADIR


After bdr_init_copy finish, you can delete the init node with the following command: 

SELECT bdr.bdr_part_by_node_names(ARRAY(SELECT(bdr.bdr_get_local_node_name()));


This works ok in our installation. 

Regards