Slots For elemental plants

In my opinion, the game progression is great. We no longer need to grind for hours to unlock plants, but I think there’s one major issue: compared to PvZ 2, PvZ 3 gives us much less freedom in choosing which plants to use.

For example, in the Sewers, Lime Bomb is useful against many zombies, but to use it effectively, you may need to bring Puff-shroom, which itself requires Sun-shroom and Peashooter. This means you're using 3 slots just to have one plant to deal with it's principal environment 

This becomes especially restrictive in levels with multiple special zombies. If you have to deal with flying zombies, miners, blockers, and other mechanics at the same time, we end up forced to use cendurian or lychee and hope it works.

My suggestion would be to add separate slots for what I’d call “elemental plants”: plants that are primarily useful because of their merges, and this way we could choose more necessary plants, than just use one single type of plant and hope it works.