Multiple Collections in Multi-Reference

The ability to select entries from multiple collections in a single multi-reference field. The relationship field in Podio works like this and it is very useful. For both a single and multi reference, it lets you select multiple apps(collection equivalent) to be able to relate to(select from) e.g. let’s say I want a ‘related articles’ list on a product/service page, I would have a multi-reference field that allows selection from any of my blog, news, case studies, reviews collections, instead of having to have a separate multi-select for each collection, and multiple lists on my product page.