Is it possible to use one certificate with aliases for MongoDB cluster?
Actually, yes : 
https://docs.mongodb.com/manual/core/security-internal-authentication/#x-509


  Either the Common Name (CN) or one of the Subject Alternative Name
  (SAN) entries must match the hostname of the server, used by the other
  members of the cluster.
  
  For example, the certificates for a cluster could have the following
  subjects: subject= CN=,OU=Dept1,O=MongoDB,ST=NY,C=US
  subject= CN=,OU=Dept1,O=MongoDB,ST=NY,C=US subject=
  CN=,OU=Dept1,O=MongoDB,ST=NY,C=US