Set sub-task FixVersion when dragging it's parent Story to a version in Agile Plan Board

I use Agile boards heavily and often use JQL filters to display tickets across multiple projects (e.g. One corporate initiative has tickets in several Jira projects and the sponsor wants one Agile board to look at, not 10). The problem I have is that there is no reasonable way to include sub-tasks, from multiple projects, in you Agile Work Board.

Example:

• Project A has a sprint that includes tickets relevant only to the team (e.g. code refactoring) AND to a corporate initiative (e.g. deliver dependency A to team Z)
• Project B has the same situation

There is no JQL that I can use to create an Agile Board that displays the sub-tasks relevant to the corporate initiative in both projects. If I use "project in (Project A, Project B)" I get the refactoring tickets. If I use "fixversion = 'Corporate Initiative'", I don't get sub-tasks because they don't inherit the FixVersion of the parent when you drag-n-drop on the Agile Plan Board. And I can't use "Epic Link" in my JQL because you can only set one Epic per ticket and I can't force teams to put all Corporate Initiative tickets into a single Epic or they lose a lot of value from setting their own epics.

So what to do?? I can't think of any reason why a sub-task would not inherit the FixVersion from it's parent when it is dragged onto a version in the Agile Plan Board. It would be a gross violation of Scrum principles to say that the parent is being planned into a release, but the sub-tasks are in a different release.

The worst part about this is that there is no way to use JQL to find the relevant sub-tasks so that you can use Bulk Edit. You basically need a nested JQL query like this:

parent in (fixversion = "Corporate Initiative"))