Ditto may be gimmicky, but with the lack of a Normal typed mega... sort of need the ability to throw out something to counteract opposing Megas. So with that, Wiggly and Chansey are out, leaving me with this new set up:
Staraptor: Ace / Anti-Fighting
Heliolisk: Special Sweeper / Anti-Ghost (Dark Pulse)
Ditto: Ditto dittos.
Snorlax: Hardy physical pivot
New:
Stoutland (Replacing Chansey): Hardy special pivot (packing Intimidate and Assault Vest w/ Crunch, Retaliate, Play Rough, and Superpower)
Cinccino (Replacing Wiggly): Speedy Paraflinch w/ U-Turn (King's Rock and Skill Link w/ Tail Slap, Rock Blast/Bullet Seed, Thunder Wave, U-Turn)
Important Notes: Snorlax will have Thick Fat with either Thunder Punch or Rock Slide, and will be my primary way of dealing w/ Talonflame. My team has multiple Dark type moves. Staraptor and Stoutland both can deal w/ Fighting types (Flying and Fairy), and Snorlax will have Zen Headbutt too. I KNOW Ditto is gimmicky, but he's a solid choice if you know how to use him well.
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My Gym Sign-Up. :3
Pokemon: Arbok, Vileplume, Gengar, Ariados, Weezing, and Dragalge
Gym Type: Poison
MegaMon?: 1 (Gengar)
Ace: Dragalge
Badge: Venom Badge (A purple, droplet shaped badge, outlined in black)
I know how you feel about the mega being tossed into Ubers, but at least you have the option for Megasaur. Pro: Only weak to Flying and Ice (not common solutions to an all Poison team). Con: Not half as good as Uber Gengar.
I'm surprised you're not using the classic Special Attacker Nidoking. W/ Sheer Force, he's a beast. Your team is totally different than the Poison team I'd build. I love Crobat too much, and I'd throw in Nidoking and Scoliopede (Sp. Attacker and Speed Passer), and top it off w/ Drapion for Psychic immunity. It's hard to argue with Weezing though, he's one of the best pokemon to represent the Poison type. ^.^ I guess that makes a team of 6 (if you count Megasaur...). However, your team has some flavor and is probably built around each other's weaknesses, where as mine is a "who's who" list of popular poison types.
However, if your team relied on Uber Gengar to function well, I'd reconsider the whole team rather than just trying to patch his place. An impossible task if there ever was one.