PvZ3 Evolved Suggestions:

HP Based Waves instead of Time Based

Longer Levels

PC Port or Google Play Games for PC support

More seed slots (6-10)

Imitater

Shovel

Arena (maybe?)

Vasebreaker, I Zombie, Last Stand Minigames ( also maybe)

More time before the first wave.

Currently, I don't really find much wrong with the game honestly.. these are my suggestions that  100% are objective improvements, which I don't think most other PvZ fans would disagree with that statement.