The closest that can do both is probably MPCNC (https://docs.v1engineering.com/mpcnc/intro/).

it is built with that modularity in mind but as other commenters have pointed out building something for rigidity makes it slower and heavier. a cheap 3d printer like an Ender 3 in addition to the MPCNC makes more sense, especially since you can save on the MPCNC by 3D printing the components yourself.

The main benefit to swapping a 3d printer head onto the MPCNC would be the pretty massive XY size you can build the MPCNC out to. If you need to print really large, flat objects it is probably cheaper than a lot of alternatives. But at that point it probably would make more sense just to mill it out of wood anyway.

no. anything that is strong enough to, say, CNC will also be very slow for 3d printing or laser. different processes demand different designs.

Depends on the price class, of course. If you spare no expense, you can employ lots of iron and lots of power to throw around the iron.

https://youtu.be/RcansEmVknA?t=150s

For context, that DMU50 mill is about $275,000 new.