One Pokémon that I would suggest is Blissey. I know that this one is better in terms of competitiveness, but it's honestly not that bad in-game, either. Once your team is at a corner and you need something to back yourself up so that you'd have time to recover and whatnot, you're always able to switch over to this Pokémon. Its health are huge, so it shouldn't have any trouble withstanding any hit and buying time.
For moves, I would suggest Wish, Seismic Toss, Protect, and perhaps Toxic. With Wish, you could recover any of your Pokémon's HP at any given time; this especially helps when you don't have recovery items in your backpack. With Protect and Toxic, you're able to stall, and with Seismic Toss, you could hurt your opponent and take them down bit by bit. As for item, you should probably consider Leftovers.