We made a deep analysis about the needs of several machines, the most populars such as Commodore, Sinclair, Atari and others, and we figured out that the voltages needed overall where not so different: +5v +12 +9v (unregulated) -12v and 9vAC. For any of the voltages we verified the maximum amount of power consumption and we sized the project consequently, with a bit of margin.
 
We also thought about a situation with several machines connected at the same time, anyhow connected and ready to use without the need to connect or disconnect cables. Finally, here it is the "ultimate" power supply idea, able to connect up to 4 different computers fully controllable one by one. Obviously we have to multiply by four all the available power, focusing on a reliable switching system.