@Joshua, you could still hack three inner shadows to simulate a three stroked box.
But I hate that it’s still a hack – and a tedious one at that!
@Figma, I get that vector networks (as you call them) make it more difficult to allow for CSS style borders on objects. But we don’t need CSS borders on those objects (keep what you’ve got on free vector forms because it’s powerful – and more akin to SVG).
But anything that is a rectangular box at its core (namely any Figma frame whether rotated or rounded!), it is completely analogous to any regular HTML DOM element that can take border properties. So please let us use independent, per-side stroke properties specifically on frames (much like we can for corner radii). Vector networks already do something different than frames anyway, so we don’t need it there and you can keep things working exactly the same for those.