I'm all for it. If it works in game, it's extremely strong, and pretty much invalidates most teams. However, unlike gen 6 assist there are immunities to consider. At first I was thinking it was managable because of that, but:So i just thoerymonned real quick and I think i stumbled upon the next quickban
The only reason I don't want to go through with this right away is because I'm not sure if Assist can call them in game. Paging ih8ih8sn0w as the only person I know who can confirm for us.
opening up discussion for quickban of assist
252+ SpA Water Bubble Primal Kyogre Oceanic Operetta vs. 252 HP / 252+ SpD Eviolite Chansey: 415-490 (58.9 - 69.6%) -- guaranteed 2HKO
This isn't even with specs, so you can either go for the OHKO with that or go scarf and actually outspeed things.
Every team needs water absorb+Chansey or desolate land to not lose to assist.
But you also need a dark type, or you lose to MMY with Genesis Supernova. And a Ghost Type to beat Pulverising Pancake. And a ground type (lightningrod is mold breaker bait) to beat the three electric ones. And a normal type for Soul-Stealing Seven Star Strike. And a bulky dark resist to beat Malicious Moonsault... wait, no- You need a fur coat mon bulkier than Mega Audino, a Fur Coat dark resist (like Mega Audino), or Scrafty.
252+ Atk Choice Band Adaptability Mega Tyranitar Malicious Moonsault vs. 252 HP / 252+ Def Mega Audino: 235-277 (57.3 - 67.5%) -- guaranteed 2HKO after Poison Heal
That's a minimum of 3 slots to check one archetype with a fourth probably neccesary to ensure the previous don't break down (Like Water Absorb 100% Zygarde, or similar), not to mention how you might run out of PP on one. And then your team has to deal with the imposters they can effortlessly slap on, and unless you're good enough to run, say, WoW PH scrafty as your dark wall that's another 1-2 slots. Beating Assisted Z-Moves basically requires that you lose to any other team, and even then you risk losing to a Pulverising Pancake team that carries an MMX with Mold Breaker Ghostium Z Shadow Force to KO your fur coat Giratina, or one that decides that reliability is for scrubs and they can run Soul Stealing Seven Star Strike and Pulverising Pancake on the same team, or that their Chansey also carries 10,000,000 Volts Thunderbolt for their MMY to call on and KO your Yveltal.
TL;DR: Beating Assisted Z-Moves requires a team built around it, and even then you can lose if you get unlucky or worn down. If Assist can call signature Z-Moves, ban Assist
E: ih8ih8sn0w has come through that it doesn't, now I feel silly for writing this up