Actually I will be doing a presentation at a school this Wednesday and what I have done is just parallel 2 batteries together to give me longer run time. You can get the connectors from a hobby shop or from Radio Shack.
I’m gonna try using a bunch of the LM338 (sister of the LM317, but 5A rating) with an ATX PSU to supply like 5 to 6 rails of 8+v, and allow adjusting from 7 to 8.5V. With digital voltage meter (switchable). Each rail ends with a connector to plug into vex controller or remote. No current limitation at the moment, though I may add a thermistor to reduce voltage when the 338s heat up excessively or something else innovative. No fuses, as I don’t want to run around replacing fuses.
As mentioned above, the Vex Controller can output a MAX of 4 Amps for ALL the Motors, so the 7.2 Volt supply will need to provide a little more than that. The Vex Transmitter you will have to make an “educated guess” on its power requirements at 9.6 Volts.
For “working on a bench”, I think this is a real good idea. I also place my Vex on “blocks”, so that the motors can run, and not have it drive around the table.