Unity UI Apply global theme / skin to all default UI elements

Hi,

I was wondering if there was a solution to customize Unity's default UI component.
This is something that was possible with IMGUI System but I found no built-in solutions for Unity UI.

It would be awesome to be able to change the font of a button or its background texture without having to reflect these changes to every buttons in the game. Basically I'm looking for a solution that will work the same way a CSS stylesheet does. You make a change on 1 component that belongs to the desired class and this change is reflected on every instances.

Prefabs does not work as the whole world is waiting for...Nested Prefabs.
I looked on the asset store as well but most solutions does seem to offer this capability (color palettes are everywhere but defining/applying style simply and effectively on a UI element seems to be a different matter.

Has anyone tried something like UI Styles beside the old reviews that we can find on the asset store page?