Just a thought. Why not just make a short Z that’s just big enough to hold the laser? Aren’t these things mostly fixed focus anyway? Maybe give it whatever travel the tool holder mounting plate gives, and do any bigger adjustments with a thicker backing plate under whatever you’re cutting. You could then do away with the Z motor and just put a locking knob on top. Should save quite a bit of weight and let you move faster. When you want to do the router thing, just unscrew the laser carriage off, and screw the taller router z assembly back on.