You can buy a USB to MIDI cable that in theory does what you want. I don't use one because my midi controller has a USB MIDI port.
I have successfully used that midi controller to send USB MIDI to the Player and change to any of the five presets in the ten banks.
Player does that by receiving PC (program change commands) 0-49
I don't know if it can receive other MIDI commands although the other Kemper devices are quite robust in that department and it is unlikely Kemper would have removed that from the programming of the Player.
I don't have any experience with the GigRig G3, if it sends PC numbers then yes it should work, but I think you have to use the 0-49 range of PC commands since there doesn't seem to be a way to assign different PC numbers to the Players 50 'presets'.
Tried it all with Airstep.
Does not work.