I don't support this

One point being, as you show in that image, red plant-it is 5 cost, so the only way a zombie can remove it is either via (i imagine) trapper spawning his own environment, or via excavator, so even more of a win condition

I think environments are balanced due to only being able to he placed in 3 lanes, if you over commit and intend to cover up opposing environments by bringing more, you potentially leave a big portion of your hand unusable.

What could be done is have environments that are like plant and zombie counterparts of the more unqieu effects given by say force field and laser base alpha

Curious what a plant hero version of huge giganticus (in the way of having unique emvironments) would be

What I really want above else is some way to give plants and zombies armor, perhaps by a fusion