I feel the best Trick Room teams are ones that work whether inside or outside of Trick Room. In the sample team I posted above, the second mega was Charizard, rather than Mawile. Mawile may be somewhat better than Steelix, but they do the same thing so it's somewhat redundant. And it worked because Cresselia worked well with both megas. Cresselia worked with pretty much everything back then, but sadly it is more easily beaten now, and not as common. As for Z-Moves, I can see it being useful on some Pokemon, such as Azumarill, Araquanid, or Rhyperior (and Wishiwashi or Torterra if you really want to go hardcore). Needless to say, being able to take out a Pokemon early without having to boost is extremely useful.
Another thing to worry about is that certain Pokemon, like Porygon2 and Mimikyu, are using Trick Room on balance teams, just to mess up with fast sweepers such as Salamence, Blaziken, Charizard, Volcarona, etc. The downside to this is that some of these mons can cut your Trick Room sweep short by using Trick Room themselves to reverse the effect. P2 is quite bulky, and Mimikyu has Disguise (and sometimes Focus Sash as well) for insurance.
I haven't tried Trick Room this generation yet myself, but these are some struggles I suspect will face our Trick Room teams.