My 2 cents: It kinda seems to me like 3d printing is illegal so that vex can continue to make profits off of gears and gussets. (They do need to stay in buisiness tho so is that really a bad thing???).
But this already happens with lexan and cnc machines. For example this during turning point:
(Taken from Here )
My point: Adding 3d printing isnt going to unbalance the playing feild more than it already is.