Can a full size router be used ? Or is it the weight ?
Size and form factor also play a role, and the fact that it really isn’t necessary for the loads that we run. There are some limitations with the motors that we use to push things around, and if you use a larger form factor tool, that takes up space in the machine’s footprint that now you can’t use for the actual work.
In short, you CAN use a larger tool, but it will take you some more work to design your own tool mount, and may interfere with the CNC operation. I’m pretty confident that my LR3 could lift and move around my large router… but I still have a Makita RT0701C strapped to it.