Oh, crap. You just need a Sapphire Game, sheesh. I suggest not. Since the rewards after completion are not worth it. But it's your game. For me, I already have all 3 Johto Starters.
though it is unethical, if none of your friends are willing to let you borrow their sapphire (assuming they have it) or trade you a lunatone, i say go ahead.
Off topic(ish): do you think it would be ok to cheat a shiny bulbasaur i got cheated into losing