Can default object names be changed?
What kind of parametrization/external programs could be used to
  achieve having such a name as default, when for example using a create
  table statements which mentions the fk but does not explicitly provide
  a constraint name?


There's no way to change the default name generated when the DDL doesn't contain a name.  The only thing you can do is to run a batch process to identify non-compliant objects and perhaps drop and recreate them.