If I were Misty...
1) I would get both Staryu much stronger. (during the 10th special, Staryu didn't look terribly impressive)
2) I would ATTEMPT to teach Psyduck how to swim!
3) I would teach Starmie some other move besides a Water-type attack, such as Psychic (duh) and heck, maybe even Thunderbolt!
4) I would train at the Seafoam Islands, just like FireRed and LeafGreen claims.
5) I would overall get stronger to show to Ash that I AM a Water Pokémon Master! (or at least getting there...)
6) I would try to at least appreciate Ash's accomplishments verbally. (she never did during the show)
7) I would invent new ways of preventing Brock from flirting with girls. But ear pulling is just fine.
8) I would redesign the gym. A giant Dewgong on top of the gym is just silly-looking.
9) I would travel to Johto to Millenium Town and bring back the Pichu Brothers and their friends back to Cerulean City! (hey, nobody can have too many cute Pokémon, right?) Actually, that's what I want in real life!
And most important of all...
10) I would learn how to cook!!!
Boy, do I feel sorry for Ash and Pikachu for trying THAT pot of stuff out...
I actually can agree with Misty's decision for staying at the gym. Everybody's gotta recollect their feelings sometime, ya know.