I did think about this but after some thought came to the conclusion that it was a lot of trouble for little gain:
1. You need to ensure the two items are reasonably well balanced to be able to flip them easily
2. This is likely only possible with only very small tools - even small bandsaw is 700 - 900mm high, small pillar drill approx 700mm
3. Assuming they flip/rotate around a pivot/bar fixed to the centre top of the cabinet which is (say) 600mm deep, the cabinet would need to 400 - 600mm away from the wall to allow the bandsaw to rotate
4. The cabinet would need to be around 950mm high to take a bandsaw - eg Axminster 250n. This may leave the machines at the wrong working height.
4. If the pivot was at the front of the cabinet, you would need to fight the weight of the machines to rotate.
There may be some more elaborate solutions with a gear operated rotating mechanism etc. However if space is an issue it is much easier to put each machine on separate cabinets fitted with lockable castors and simply move them as required.
Terry