I was asking myself the same question and found a way to do it and without code.
In the new collection “featured elements”, I created a switch field just like you, and 3 reference fields for each of my collections (video, documents and press).
Then, inside this “featured elements” collection, I created 3 items for each of my collection (video, documents and press).
For instance, in the item video, I choose the video I want to feature with the reference field. I don’t touch to the other reference fields. I use the switch field to feature it.
Then on my template, I add 3 collections lists above each other, using absolute position. I use a filter on each of these collections to show its only if the switch field is on.
And it works !
You just need to be very careful with the switch field, to make sure that only one of the item is switch on.
Hope that what clear enough.
If someone else has another way to do it, let me know.