Honestly, the four move limit is there for a reason. With eight moves, Sweepers would be completely dominant because it'd be nearly impossible to predict what moves they'd use. No matter what you break out, they'll be able to trump it unless their movepool doesn't allow it. Meanwhile pokemon with limited movepools will almost all fall into the NU category because they just can't keep up. C'mon, Flareon's got it bad enough as it is.
That being said, it would be a benefit to a few types. Paraflinchers and Walls, for instance. However, I'd really set the limit at six moves instead of eight, because eight is just plain too much. The whole point is to be forced to pick and choose what your pokemon can do.
Anyway, my opinions on a double-stuffed moveset aside, I think I'd most likely use a Togekiss for this type of thing...
;468; Togekiss @ Leftovers/Life Orb/King's Rock
Nature - Timid
Ability - Serene Grace
EVs - 6 HP, 252 SpAtt, 252 Speed
- Substitute
- Thunder Wave
- Air Slash
- Aura Sphere
- Water Pulse
- Encore
- Nasty Plot
- Wish
Substitute is pretty obvious. From there, it depends on what the enemy does to the Sub. If it uses a non-attacking move, Encore it and Togekiss can Nasty Plot to its heart's content. If the Sub gets attacked, Togekiss can Wish, set up a second Sub when the first is knocked out, then Thunder Wave or Encore the enemy while the HP from setting the Subs up gets recovered. Thunder Wave, of course, sets up for Paraflinching, with Air Slash having a 60% shot at flinch. Water Pulse can deal with other threats, and adds on a 40% chance of confusion. Aura Sphere will deal with threats to Flying types as well as conquering Steel and Dark.
