This is NOT about pipes and YAML alias and anchors.

We require to share the same/similar bitbucket-pipeline.yml files between repositories.

Requirements:

• the build must be centrally managed 
• the templates shall be able to be customized 
  allow overriding variables
• the solution shall not rely on maintaining docker images
• A solution similar to gitlab-ci includes is preferable 
  https://docs.gitlab.com/ee/ci/yaml/includes.html