Meganium doesn't have a lot of good options, sadly. You should remove Bullet Seed and Sweet Scent, replace them with Earthquake and maybe Body Slam if you want to go as offensive as possible, or Sleep Powder and Synthesis if you want to make it more defensive (though I wouldn't recommend it since that would leave you with just one damaging move). You can also replace Grass Knot with something else such as Seed Bomb or Energy Ball depending on which move you prefer.
Blaziken on the other hand, has a lot of awesome options. I recommend Sky Uppercut as a Fighting move, which it learns at level 59. And if you are interested in changing its remaining moves, I have some suggestions for those too. For a Fire Move, you should go with Fire Punch, Blaze Kick or Flare Blitz. For the final moves, you can choose between Brave Bird, Stone Edge, Rock Slide and Thunderpunch for offensive moves, you can also use Swords Dance to raise its Attack. Or maybe something else if you would prefer that.