I agree with that. Though the screws inside seem a good idea at first and even the connecting plate could be made quite stiff, there are some small details to be considered.
Like:
-tightening the motor belts and later visually inspecting them constantly. Ones inside it would be difficult to notice something is not right
-adjusting all that contraption, once the machine is heavy
-screws outside are almost at the ideal height for cutting with very short to none arm, to drive the gantry, once inside the arm becomes big, needs additional strengthening which may lead to need for Servo motors due to too heavy gantry

In short- all could be done but on a first build i would aim for simplicity, proven designs, easy to adjust. raising the sides of the table is not ok if you are in a production workshop and need a machine to lift heavy plates to the table. All else is a preferred design, shorter to none gantry legs and additional dust protection. Its proven, dust will not go on screw even without vacuum cleaner.