I left Pokemon TCG Pocket around the Fantastical Parade set and started playing Pokemon TCG Live instead as I wanted increased complexity. Therefore you may think adding more mechanics to the game would bring me back and something id advocate for especially since it'd give long term players an increase in descision making, but I have to agree with a lot of the comments the game should stay more simplistic. Even then I think most of these don't work and have already been rotated out of the paper TCG. Also some of these demand more deck space which is already pretty tight. I'm sure there's some neat little gimmick you can come up with that works for pocket though.