Here was my attempt at it, I had one free evening and I went about 30-6 or something.
I was using Lanturn for this challenge, a ResTalk set that worked amazingly well, especially against the Rain Teams that I was seeing a lot. Lanturn is hands down one of the best answers to the combination of Tornadus-T / Thundurus-T / Genesect, and it was really fun to use. I really didn't have any trouble against Rain, but Sun was a pretty difficult matchup. Basically my team was just random hyper offense with a Lanturn for Rain. I had a Rock Polish Landorus for Sun, and Specs Keldeo / Scarf Genesect / Sub SD Terrakion core, with a lead Mew. Hyper Offense was something I've never used before, but it worked pretty damn well. I'm thinking it's the best weatherless playstyle to use, as it performs well against most weather teams. The MVP of this team was definitely Lanturn. Honestly, if you need something for Rain, use this. I definitely need to start using Hyper Offense more, it's crazy fun to use. Thanks for Birkal, Pocket, ginganinja and alkinesthetase for setting this up, and everyone else involved it. I might ladder at a later time to see how much higher I can get, we'll see.