Give the ability to have cross-project workloads (estimate, actual and remaining) consolidation.
Example:
Project SOL is a "Enterprise Solution" project, involving several applications.
Project APP1 is a first "Application" used in this "Enterprise Solution".
Project APP2 is a second "Application" used in this "Enterprise Solution".

APP1 and APP2 need their own projects to manage their own issues, components and releases.
SOL needs its own project to manage Solution Requirements and any other Solution-level issue.

When a requirement is created in SOL, we would like to be able to link involved software change in APP1 and APP2 (already works fine with issue links) and consolidate workloads at the Solution requirement level.

This feature now exists when the linked issue is a sub-task. Workload is actually consolidated at the main task level and included in the workload progress bars.

We would like to have the same behavious for cross-project issues.

Linked issues' sub-tasks workloads should be included in the total.

This could be done by adding a "consolidate workload" attribute (boolean) at the issue link level, and then use this attribute to determine which issues to sum when calculating the workloads consolidation.

Pay attention to avoid endless loop.
Pay attention to count an issue workload once only.
Jira is not an accounting tool, don't bother with duplicate counting when an issue is linked to several parent issues, just count it once per parent.

Possible improvement: bother with the "several parent issues" double counting and add a second attribute "consolidation percentage" at the issue link level.