If you run pulleys to do a core-XY or an H-bot, that could be a mess quick. If you have two rails that hold the rails for the X,Y movement and the extruder, you have at least two motors (bowden setup) and their momentum to deal with which means slower print speed. You have to coordinate the movement of all hotends so they do not run into each other and you have seems to deal with. I can see how that would all be a rather tricky bit of research.
The addition of new filament properties like filament that expands to a specific size when heated to a specific temperature makes for some interesting possibilities like reducing infill by making the filament expand. The ability to add multiple nozzles to the same heater block so you can use different colors or nozzle sizes to the same block does too.
Here is hoping the person is healthy and well. This pandemic with its loss of health, life, jobs, homes, etc is a pain. I just hope the person is well.