A Little Rant first:
I've been playing BH for nearly 3 years now and am so glad that all these new SM abilities + Pokemon were added to BH for new, diverse playstyles. Many common playstyles/abilities you can use in the meta have hard counters, like Rock/Paper/Scissors, and this hard-countering (at least in my experience) is what makes BH healthy: you build your team around how you want to play and make counters for what you're usually up against that gives you trouble. Listed on the left below below are a few common playstyles I have used and gone up against throughout the many battles I have played, and on the right is their hard counters.
Priority Moves vs. Queenly Majesty/Dazzling/psychic Terrain
Sleep Talk,Comatose,Whirlwind (with hazards up) vs. Magic Bounce
Contrary (or any stat boosts, rather) vs. Topsy Turvy/Spectral Thief
I deem Crystal-free Z-moves unhealthy due to their lack of counters in general that can successfully wall them (there are some, but to always have to run the same counters on every team drastically limits team-building). All it takes is a STAB Genesis Supernova from a fast, hard-hitting Psychic type (like Deoxys-A or Mega-Mewtwo-Y) to knock out your pokemon AND get Psychic terrain up so you can't use priority to revenge kill (and for 4-7 more turns after that), and after you finally knock the opponent's z-move pokemon out and the psychic terrain is gone your team is in shambles and you pretty much cannot come back from a huge deficit like that.
For all those reasons listed above, I will have to go with
BAN