I can see where you are coming from here, nice idea and would certain strengthen it 100%.

But as always there is a negative - it would stop me being able to fit the aux spindle.

By having the support on the end of the quill when running as a normal bridgeport, I would maybe lose 12-15mm of travel - not too bad. But to allow me space to fit the aux spindle as well below it, the support would have to be that much further up the quill, probably losing 40mm + of travel permanently - this would cause big issues when doing normal work.

But it is a nice idea though.