The thing that I like most about Z-moves is the fact that they don't seem mandatory when team building, which will do a lot for fighting the Power Creep.About Z-Moves: They're one per game, so I believe they will have a weird mechanic. I actually don't bother too much about them because I honestly believe they wont be too frequent on the meta, here and VGC.
Although I think we may want to count Gems out, now that I think about it. Z-Moves do form such a similar function that Nintendo may be essentially replacing them