I'm not one to steal ideas usually but something close to the chocobo system from ff9 would make me love gk :P
Hatch your own chocobo like thing, use it to find certain treasures from treasure maps to get points to upgrade him to different colors. Eventually your chocobo would turn blue and be able to swim (maybe a bit slower than a boat) and be able to fly (like teh zepplin probably ~o~). So many things you could do with it lol.
You'd be able to call it with a certain song on your flute...
I doubt it'll ever happen tho ._.