I don't think I ever used items in Pokemon beyond Pokeballs and Repel. Then again, I only played Generation 1 so that might have a lot to do with it.

On topic: I've never tried it, but then again, I don't really care for sequence breaking in a game, and I happen to like watching the escalation of Squall's Limit Breaks. I never tried Disc 1 Lionheart or Disc 1 Omnislash in VII either. Both games are pretty easy without seriously borking the game.