I've made a total of 3 playthroughs. Then, I just finished a play-through using some hard-mode hack.
The first time: I've made a Poltergeist team. Rotom would have been in the team if I could meet him before the league, but oh well! Starter was Oshawott, and discarded him as soon as I got my 6th Poltergeist pokemon.
The second time: Heavy pokemons. Shaking and Dust ahoy when sending my pokemons in a triple or rotation battle! Starter was Tepig, and kept him in my final team.
The third time: Volt-Switch and U-Turn! Lot of fun with switching! Starter was Snivy, and again, discarded him as soon as I got my 6th pokemon.
The fourth time, with Hard-mode: Auto-meteo team. Since most of the 649 pokemons were available before league and that they could learn their Dream World ability, I took the opportunity for this team.
Next game I'll make, I think I'll make a Metronome Challenge. Could be lot of fun!