For you psychic type, I would suggest Gallade or Gardevoir, because Ralts you can get just before Petalburgh, whereas Abra is a pain to catch because of Teleport and Meditite you can only get in Mt. Pyre. Between Gallade and Gardevoir, I would lean towards Gardevoir because of the slightly more advantageous typing, but if you like Gallade better than go for that.
For your Rayquaza replacement, I would suggest your starter, preferably Swampert or Sceptile (Blaziken is redundant on your team). You need something with Surf to get around Hoenn, so Swampert is the better choice for your team, even though you'll get a Dragon with Mega-Sceptile.