If the ending is programmed to respond to chord changes, I think you should be able to play the ending in the key of G as needed.
If the ending isn't programmed to respond to chord changes, you might be able to copy the style to a new style and edit the settings for the ending-- or if necessary, you could use a MIDI editor to transpose the notes of the ending to the key of G.
Are you playing one of the internal styles, or an external style?