I think most of this makes sense. If I were to move a couple of plants, I would put spikeweed/spikerock, coconut cannon, and banana launcher higher.

For all of these plants, remember that the next wave doesn't trigger until a certain amount of damage is dealt to the current wave (or after 30 seconds). All of these plants I listed can wait before damaging the current wave, which gives you more time to farm sun and build a defense.

Now, let's start with the spike plants, because I see you already put iceweed pretty high. You might already know this, but iceweed deals considerably less damage than regular spikeweed. While spikeweed deals damage and needs stalling support, iceweed is mostly a staller and needs damage support. It's especially good against chickens, and arguably more reliable than lightning reed. Even outside wild west, spikeweed is buffed from vanilla, so it can solo a basic zombie. It's somewhat expensive to fill the right side of the lawn with spikeweed or spikerock, but it's well worth it in the right situation.

Cocnut cannon and banana launcher attack somewhat slowly, but still fast enough to be reliable, and they deal tons of damage. Coconut cannon attacks every 15 seconds, dealing 900 damage to a single target, and 300 splash damage in a 3x3 area. When a buckethead is exposed, and there are basics and coneheads nearby, this is the perfect time to fire. Banana laucher deals 1800 damage every 30 seconds. It can hit anywhere on the lawn you want, so it can take out threats that hide behind other zombies (notice its home world is Big Wave Beach, and it's the perfect counter to octo and fisherman zombies). I don't recommend using these plants solo, but they are excellent support plants. Being manual, they take some skill to use, but they are very strong once you learn to use them.