Embedding a component without slots as a slot within a larger component

[staticshock]

I was just trying to combine the Switch styles in the RAC starter kit and ran into a problem: if I turn track into a slot, it can't as easily extend focusRing anymore. Here's what I have so far:

const switchStyles = tv({
  slots: {
    base: ...,
    track: [
      focusRing.base,
      ...,
    ],
    handle: ...,
  },
  variants: {
    isSelected: ...,
    isDisabled: ...,
    isFocusVisible: {
      true: {
        track: focusRing.variants.isFocusVisible.true,
      },
      false: {
        track: focusRing.variants.isFocusVisible.false,
      },
    },
  },
})

This works, but is kind of verbose. Is this as good as it gets?

I looked through the docs and didn't find any way to "embed" an existing non-slotted component as a single slot within a more complex component. On a whim, I tried this, but it did not work:

const switchStyles = tv({
  extend: {
    track: focusRing,
  },
  slots: {
    base: ...,
    track: ...,
    handle: ...,
  },
  variants: {
    isSelected: ...,
    isDisabled: ...,
  },
})