Self-soldering circuits:
@FourOh-LLC it would be interesting if he could make the resistor layer with little short circuits that get in circuit only at a slightly higher temperature than the solder on top melts. Then, you could use the layer to melt the solder, after that kick it a little higher voltage to melt the parts and short the resistor, use current limiting to protect everything when the short kicks in, then turn it off. The resistor layer could become your ground plane, so you don't need another.
I think the resistor layer might interact poorly with some RF, but there's probably some way to write software that automatically avoids that issue.