Brief title for your desired feature: The "special nets" menu should include a "preferred layer" for a given net. How would you like the feature to work? The pathfinding algorithm for the autorouter would consider it drastically "cheaper" to put a net onto the preferred layer. It would still use any layer it has to to complete the routing but if possible it would use the preferred layer. Why is this feature important to you? It makes it simple to use all the copper on the board with minimal human labor. Just tell the autorouter to "prefer" the top of the board for ground (since most chips have more connections to ground than VCC), the bottom of the board for VCC. Then, flood fill. Those traces for ground now get to use the entire remaining layer of the board for maximum conductivity, and vice versa for power. This feature would work even better if the GUI were designed to suggest this or make it easy. "autoroute, with GND to top and VCC to bottom, followed by flood fill top and bottom set to GND and VCC respectively" is probably the best way to make most simple boards.