Ooh goodie goodie. I've got a few ideas...
1. Seed packet drops. Whenever a plant defeats a zombie, or a zombie is defeated with some form of assistance from a plant, there is a chance that plant's seed packet will drop for collection. This will encourage players to play with all of the plants, developing new strategies and combos in the process.
2. Trade 4 Plant Food to replace a mower in Endless.
3, 4, 5, 6 & 7. Bring back the gem drops.
8. Remove the leveling from Adventure to restore the balance, and unlock all premiums for Battlez. Seed selection is small enough in Battlez that players can't get too crazy with premiums at their fingertips.
9. Bring back the gem drops.
10. Environ-Mint. Power Mint that boosts plants that belong to the world you're playing in. Also creates tiles from any other world (power tile, gold tile, Plant Food or sun grave, etc). Environ-Mint can't be selected with other Mints, or doesn't stack boosts from other Mints. Create a 12th world that has premiums unlocked within it. Environ-Mint will boost premiums in that world. Use that world to FINISH THE FRIGGIN STORYLINE. I haven't figured out Environ-Mint in Battlez yet.
All that, then I have a bunch of world and plant ideas just aching for some exposure.