As always, I find issues and tweak my plans over time. As a result, your move likely will have to be altered since Unicorn is presently exposed to Aipom's Swift as presently constructed. As a result, I'm proposing you alter your move from K14 to L13 such that you attack Seviper while shielding an Ally from harm. Unicorn's advantage over Aipom and Liepard is reason enough to make this change, although if Seviper survives, there's a good probability it makes it up the Mountain unless we KO it. Mercy lobbing a Stick at it does increase our odds since even 5 damage can make a world of difference.
Robin will deal 25, dropping it to 45. If Mercy deals 5 with the Stick, now we're at 40. Then you swoop around and attack, likely dealing 25-30 with a strong Ice move. Going with a Lowball estimate of 25 puts it at 15. While it's not a STAB attack, Quick Attack from Unicorn ought to be enough to KO it. Net result is a KO'd Enemy while protecting an ally.