Thanks for bringing up Volkner and Copycat. Completely forgot about those.
VikaBulu is going to be in a weird spot post-rotation. It’s the only ‘old’ deck that loses next to nothing to the rotation, but where it’s going to be in the format completely depends on how well Malamar decks perform, as both function similarly—except VikaBulu is high-risk/high-reward and Malamar is a smaller risk but high-reward (but Malamar loses some significant cards to the rotation).
Copycat...oh boy, I don’t know. It looks fantastic on paper, but it’s REALLY finicky. It has a high-reward value, but only if you’re in a spot where you’re not pressured to use any other supporter for the turn and you just need items. Against a Zoroark-GX builds, it’s great. I’m not sure how good it is against other builds.
Hala CAN be good, but I haven’t seen or heard of many decks that are actually going to put it to good use. I did see a post either here or Reddit that listed all the Pokémon with cheap GX attacks to get Hala working quickly. There are some good candidates, but the only ones I can think of are Kartana-GX, Turtonator-GX, and Drampa-GX. So you have to center a bit of your deck around getting a quick GX attack to work AND THEN you can use Hala. At which point is just Cynthia +1. Is all that trouble worth one more card?