Zeo, you got a good point, but I think using a cloaking field generated by the Exceed's gravitional energy would make a near perfect, if not perfect, cloak. Though, I'm pretty sure a Zoalord would be able to sense the Exceed because of the energy being generated and active used.
If the Gigantic Exceed were to have cloaking capabilities, it would probably be able to generate it from a different source of energy. Albeit, I wouldn't know what the energy would be. I believe the cloak would be as effective as Gastal's invisibility.