I disagree, because if I remove @Named it works fine.

It works as expected - the deployment should not fail if you remove @Named from either EtcBpmExpressionService or EppBpmExpressionService because then there will be no ambiguous bean name.

EtcmpaBpmExpressionService disables EtcBpmExpressionService but not EppBpmExpressionService. And as Matej said - stereotypes are not inherited, therefore EtcmpaBpmExpressionService is not an alternative.