Wanted -- Select fixVersion from arbitrary project while within a different project

[daf]

I have one Project (RM) which provides some workflow and extra field information to track our product releases, and tries to leverage Jira releases for data.   When creating an RM ticket, the user will identify which Project (AA, BB, CC ...) contains the issues being fixed for the specified product release.  THEN I want to make it possible for the user to choose from unreleased fixVersions for that Jira project.  I cannot figure out how.   I can use the api to get the appropriate project list of fixVersions, but can't identify where I can store them for the user to select from.   Fundamentally, I want to populate a custom field with the fixVers I calculate and require the user to select one, but I can't seem to do that on an issue-by-issue basis.

Eventually, the goal was to populate this superset of release information WHEN people defined the fixVersion (and thus the Jira Release), but the timing of when these two things happen make that problematic.

Are there other ways to do this?

[Nic Brough -Adaptavist-]

Versions are project artefacts.  One of the things that this means is that you can't use them outside the project they belong to.

Atlassian have some motion towards having versions that can be shared across projects, but the the current situation is that any version you put on an issue must be a version that belongs to the project the issue is in.