Hi, with CNC you're transferring the accuracy from the person to the machine......if the machine is not up to it, it will never get better...…..whereas with a person you learn by your mistakes and eventually get better.
A manual mill is very forgiving because the person working it is the deciding factor, but with a CNC mill, if you go cheap, it will never become a workable entity......best of luck....I would recommend doing it up as originally designed and sell it on, the money you make will go to getting a more impressive new mill.....you can't make a silk purse out of a Sow's ear.
Ian.