Foiling is great, but...
Support for a metallic substrate? That allows overprinted spot colours.
One example being that I have had experience with a design where the customer needs a tint printed over a silver to shift it to gold, with some KO for silver wordmark, but the tint was also used with a kind of earthy tone to get a warm brown, instead of using separate spot colours. (Due to limited stations on the machine and process colours also being used in the specific market for legal requirements.)
I'm giving my 2 cents... I think the point is we need some more special FX and easy tools to apply them, despite the software we use - Origami or Koru - e.g. shiny transparent varnish, metal foil, transparent film, ... etc etc.
This sounds like a task for Owlet. After all, Origami is just a 3D folding software. We'll definitely add generation of some types of masks there, but for complex materials you'd better use proper software designed for rendering complex stuff. Especially as Origami now uses artboard boundaries for artwork export and it is not a problem to export additional masks for what you need.