No, the G-Major / G-Major does not support MIDI phantom power. A solution would be to buy an external box that provides this.
Rocktron has a 5 to 7 pin midi cable RDMH-900 that will work with any rack gear, and their All Access foot controller. We haven't tested it with other foot controllers. It has a 7 pin end to plug into the AA then a 5 pin end to go to the MIDI in of any MIDI gear. Then a small "y" comes off of this end where you would plug the AC adapter for the AA back at the rack so that a additional cord is not needed to run out to the stage.