Slaking looming

Abilities are the correct answer, or some new mechanic similar to them.

Someone suggested giving him a quick move that does very little or no damage so he essentially only had charge moves. The way Pokemon go works I think this would be the best solution. Or they could nerf him like everything else

The Safest Bets for Gen 3 article does not even mention him?

My guess is that they will make Slaking only versions of moves with half the normal power.

This is quickest and easiest way to approximate Slaking only attacks every other round.

1 * 1/2 power attacks vs 1/2 attacks * 1 Power should be close as possible.

With a CP over 4000 how long do you think he will stay motivated in gyms? He is nerfed within 30 minutes.

Custom moves that have cooldowns that are twice as long as 'standard' versions of those moves - effectively skipping every second attack.
It fits him...and it works for what it needs to achieve.

...but this is logical, so it will be something different.