A PnP placing the components upside down onto a surface printed by another head would be interesting. You could align the heights of the resting surfaces to optimise pads needing to be connected being on the same plane. I'd still want to lay copper but if you had the ability to squirt a little solder paste from (yet another) head, you could stack everything with wire connections into a very 3d circuit.

If the base material was thermally conductive you could have a heatsink block with the circuit embedded in it.