If I could have one significant new feature in Figma, this is it: container components. This is basically the Figma equivalent of the children property in React, or media placeholders in Keynote.
I’d like to define one or more “parent” frames in a component into which I can place one or more non-component objects that behave as they would if the parent frame weren’t part of a component. So if the parent frame is just a regular frame, I can, say, put a rectangle in it and drag it anywhere. If the parent frame uses autolayout, I can put three rectangles in and they line up and size themselves accordingly. And so on. You do get some of this with instance swaps but only some.