>>28386177Hundreds of VGC players have tried that and it just doesn't work very well. If doubles were a generally more defensive metagame it could be alright, but having to take a turn to skill swap, then a turn to switch out your new Pokémon is just too much time wasted, since Slaking isn't worth a regular Pokémon with two turns of setup.
Besides the fact that anybody who sees a Slaking in team preview will be on the lookout for something to taunt.