Ideally you would have two separate machines space allowing. A router need stiffness and rigidity where a laser not so much. That weight penalty would end up for a slow machine. If you were to run a low power diode for occasional small labelling work then bolting one on might be ok. Safety. Lasers should be fully encased and not be able to be turned on unless the lid is fully closed.
So, dedicated laser with a boxed in frame designed for high speed movement is my vote. Save the heavy duty frame for what is was designed for. IMO that is.