I, for one, am completely immune to this deck, as I don't need an ability to make me only flip tails! I always do anyways!
So yeah, your opponent can only flip tails with Malamar's ability, which doesn't sound frustrating at all. "But what if your opponent doesn't run any coin flip cards?" Well, I'm glad you asked, because with Yell Horn and Mienshao, you opponent will be constantly confused, and unable to attack, since you need to flip heads for the attack to work! And with Mienshao shuffling itself into the deck, you can just put Malamar in its place to put the coin lock back in. Galar Mine should help with any Pokemon that try to retreat and remove the special condition.
In case you can't tell, this deck is quite meme-y, but suggestions are still welcome!