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It has one of the best support movepools out there, including Baton Pass, but Cosmic Power seems like a waste compared to what else it can do to cripple opponents. Without any reliable way to heal itself and its typing, Loppuny probably won't be able to get many boosts off before being forced to pass/switch. It might be able to bulk up on a switch and survive long enough to kill on offensive sets, but it's not a very threatening physical attacker in the first place.
If you have a wall with recovery, but no boosting moves, maybe CP/BP might be worth it. But I'd say stick to team support. Shutting down walls, Thunder Wave, Healing Wish, Magic Coat etc. Whatever augments the rest of the team.