I would join. Although, it's like you said, it needs to be tested to see what needs to be added/removed.
I know that Rhydon will be a major problem, and as such, everyone will be carrying something like Marshtomp and Grotle to counter it.
Wartortle would be seen a lot because, as someone mentioned, he is the only Rapid Spinner here, + the fact he can take on Rhydon w/ STAB Surf/Water Spout. Wartortle might even be able to use bite if Haunter and Kadabra become an issue, but it is probably too weak, even when you consider Haunter/Kadabra's low defense.
Roselia would follow in it's Superior form's footstep. It would probably be used w/ Sleep Powder, Toxic Spikes, Spikes (or both) and Leaf Storm in a leading position like it's evo. Haunter would become a common anti-lead w/ Psychic to stop Roselia/Monferno, Focus Sash, and Explosion (just like Azelf). Monferno would also be used as a Fake Out lead to brake sashes. Priority would become near non-existent. Monferno is one of the only Pokemon w/ priority that's not Quick Attack.
lol. CB Huge Power Marill w/ Aqua Jet & CB Bullet Punch Metang. Metang would be a good lead in this tier because of resistance to Explosion from Haunter and Graveler, resistance to Grass and Poison from Roselia, and can hurt Monferno w/ STAB Zen Headbutt/Psychic and EQ as well as SR. Graveler might also act as a slow, bulky lead who sets up SR (but that won't be very common/effective because of the double weakness to grass and water).
Grovyle can use Crunch/Pursuit to handle Haunter and Kadabra and their low defenses (and possibly Dusklops), and Leafblade/Leafstorm will dent Rhydon pretty badly. Dragon Rush/Dragon Pulse or even Dragon Claw could hurt Dragonair, Shelgon, and Gabite. And Leafblade or Brick Break should hurt Vigoroth and Chansey. He can also run Arial Ace for Machoke and opposing grass Pokemon (albeit it's low BP). Thunderpunch could stop Pigeot, Staravia, etc from getting in the way. I would have to run some calculations, but Grovyle should be a really good sweeper.
I think you will have to ban Magneton before you ban Gabite......Magneton resists a lot of these Pokemon's attacks (bar Machoke and Monferno) and his special attack/defense is nothing to laugh at. He also gets Magnet rise, lowering the number of counters he has here.
The teams would look something like those in the Sunset Colosseum on Pokemon Battle Revolution (except w/ somewhat better movepools).
I just realized, Wartortal w/ HP Dark to keep Dusclops/Haunter/Kadabra from annoying him instead of bite. Grovyle w/ HP Flying for Machoke, Monferno, and opposing Grasses. I almost forgot about Hidden Power....