I've encountered the following two issues when merging multiple Pod templates:

• it is currently not possible to override shareProcessNamespace in a child template
  this happens because there is no logic for overriding shareProcessNamespace in https://github.com/jenkinsci/kubernetes-plugin/blob/f10083a42e708a6bff990c6ccb306ce618b8bccd/src/main/java/org/csanchez/jenkins/plugins/kubernetes/PodTemplateUtils.java#L341-L353
• capabilities cannot be added or dropped if any pod specifies runAsUser
  this is due to how the combine is implemented in https://github.com/jenkinsci/kubernetes-plugin/blob/f10083a42e708a6bff990c6ccb306ce618b8bccd/src/main/java/org/csanchez/jenkins/plugins/kubernetes/PodTemplateUtils.java#L222-L229