Something I've been toying around with in my mind for doubles, going to start breeding for it and see if it actually works:
Chansey @ Eviolite
Bold Nature
EVs: Undecided, considering 252 HP / 252 Speed / 4 sp atk.
-Softboiled
-Aromatherapy
-Skill Swap (?)
-Toxic / Seismic Toss
Shuckle @ Leftovers
Calm Nature
EVs: 252 Def 252 Sp. Def
-Guard Split
-Power Split
-Swagger
-Protect
By now you probably realize where I'm going with this. At this point, I'd lead with Chansey and Shuckle, have Shuckle perform Guard Split with Chansey and have Chansey become a monster tank.
I think this set up would be fine as is, but I was thinking of adding another layer to it. It's probably too much and unnecessary, but testing exists for a reason, don't you think?
So now that Chansey has a massive bulk of 168 Def and 118 Sp Def base, boosted up to 232 Def and 177 Sp Def by Eviolite in base stats, I was thinking to add Wonder Guard to her defences by having Shuckle switch out for Shedinja (provided the enemy doesn't check it) and Skill Swapping Wonder Guard from Shedinja over to Chansey.
This comes with two problems:
1) Taunt
Taunt can easily counter my entire setup. A Taunt on Shuckle in the first turn and a Taunt on Chansey in the second completely negates any tactic I want to go for. And since Prankster Taunters are pretty common in doubles, and my entire set-up is very telegraphed (anyone knows what's going to happen if they see Shuckle/Chansey out) makes it easy to counter.
2) Shedinja
Not saying Shedinja is THE problem, but it's the fact that he will be useless without Wonder Guard. I'm essentially playing with only three out of four Pokémon. He also shares bug type with Shuckle, so if the enemy decides to use a Rock Type move on my switch in, Shedinja is gone. Hence I'm wondering if it's even worth Skill Swapping Wonder Guard.