As a JIRA Portfolio user, I would like Parent Link to operate like Epic/Story so that I am able to surface issues related to larger themes / initiatives

Original request is here:

https://jira.atlassian.com/browse/JPOSERVER-1663

The key concerns for us with the current implementation are:

It's not possible to use ScriptRunner's JQL functions (or indeed functions from a variety of add ons) to find children of initiatives that meet certain criteria. With a normal link, or even epic link, it is possible to run JQL to find all linked issues where the parent issue meets certain criteria - for enterprise this is absolutely critical.
It's not possible to update the field via scripts, it's possible to do this for epic links
It's not possible to use add ons like Structure to build hierarchies as this isn't a real link type
It's not possible to use this field for any kind of reporting outside of JIRA as it doesn't extract the issue key