I wouldn't call Slacker useless, personally. Nidokings are tough Pokémon. It's just that throwing in more than one ground type in my roster isn't necessarily the best idea.

[As for the second bit... yeah, he nods, folding his arms over his chest.]

Don't know how it'd be inconvenient other than the Pokémon being more vocal with complaints. Usually Slash is pretty cool about that, though, but he's kind of determined to be seen as an equal to humans.