Nikos,
I also would like to see AS7-1769 (sharing PUs between separate application deployments). As mentioned on the forum discussion, each application that depends on the other application with the PU, will have a dependency on the PU application.
I haven't had a chance to work on this myself. The jira is unassigned so that any community contributor can jump in and work on it. I think the general idea is best described in the above forum post link.
Scott