DT, you're like a sly criminal: You know a way around ANYTHING. xD
Clefable, Porygon2, and Shedinja would work in PERFECT synergy together (I chose Porygon2 because of the better Defenses).
Porygon2 would activate Conversion2, and Shedinja would Mimic it. Let Shedinja do some damage, while Porygon2 activates Trick Room.
Porygon2 would switch out, and bring in Clefable. Clefable could use Follow Me to support Shedinja. Because of Magic Guard, any attempt to poison, burn, etc, Shedinja, would go to Clefable, and then be nullified.
Moonlight could be used when necessary, and if you aniticipate that someone will try to activate Sandstorm or Hail, then you can keep Sunny Day / Rain Dance handy, only for countering that. Finally, use Helping Hand to help Shedinja sweep, or put on Return or Meteor Mash, for damage.
In summary, this could work very well, but would only be a one-shot deal. This is the most practical thing I could come up with to match what you were saying. To top it off, I'll provide a quick overview of movesets:
Sunny Day / Rain Dance
Helping Hand / Return / Meteor Mash
Hope I helped with this idea a little bit! Sorry this was so long. xD
EDIT: Okay, it seemed longer in the submission box. :P