I suppose with the a few select high temperature polymers you could 3dprint a mold that would be capable of running a hundred or so shots before it's garbage, then use a robot to slot it into the IMM side. The mold wouldn't be capable of producing certain features though, as the injection pressures required for thinner parts would blow the parting line of a polymer tool. Certainly a living hinge would be out of the question . The cycle times would be insane, considering there would be no cooling and plastic will insulate the cavities rather than cool them, but for a short batch run I can see that possibly being cost effective - just send a file to the machine and it prints a tool then molds the parts automatically.

You could potentially do it with metal SLS too, but there are secondary operations that are required for that also, so being a hybrid unit wouldn't save anything in terms of operations there either.