You should probably add nothing or an HM slave Bibarel because 5 Pokemon is already a lot. If you really want 6 Pokemon, then I think the best one you can get is Roserade. Roserade's typing and stats are much better than Mismagius's.
Also Gyarados is a strong Pokemon, but it shares weaknesses with Staraptor. You can replace it with a Floatzel if you don't want that. Be sure to catch a high level Floatzel from a place like Route 218, Route 222, or Victory Road.
Also also Bronzong isn't that good. Its relatively weak offensive stats slow down the game, and it takes a lot of experience to level up. I'd recommend getting a Machop from Route 210 (so it comes at a high level), trading it for the Abra at Oreburgh City, evolving it, and going to the move reminder to teach it psybeam.