Ability to add any Task, Event or Campaign to a Milestone

We'd like to be able to add any Task (from any campaign), Event or an entire Campaign (this one may be a stretch, I know) to 1 unique Milestone so that we can link these multiple activities to a single traceable milestone.

This would be beneficial when building multi tactics Campaigns that are built by many different global stakeholders who have (and want) to retain their own campaigns and not having to move Tasks or Events around to other Campaigns just to make the Milestone "work" adequately.

i.e.:

Milestone name "Product XYZ Launch"

Events:

1. Customer Webinar in EMEA (Campaign 369)

2. Customer Webinar in ANZ (Campaign 432)

3. Customer Webinar in USA (Campaign 441)

Tasks:

TSK - 21556 - Email Blast (Campaign 665)

TSK - 20687 - Commercial Activation (Campaign 477)

TSK - 32558 - Social Media Promotion (Campaign 691)