Yknow, that did just give me a thought. It would be pretty interesting for a vertical level, similar to Super Mario Bros. Since WL4 doesn't have one, to that extent, it would be pretty interesting to have. We could have balloon wario fly vertically. And if he gets damaged, he could fall all the way down
Now, mind, I don't mean exclusively vertical, I mostly mean more like-- kind of like how Pizza Tower works, where your main goal is ascending, but there's plenty of left and right. The Puffy Wario segments you're talking about, I imagine a couple of them for getting access to puzzle rooms, and one more which would be mandatory for collecting one of the corner pieces.
This one could probably work like the Tower from VVVVVV with how it's structured: no horizontal scrolling, pretty much, almost entirely vertical, and (if possible) you could have Wario reach the top, quick fade, then when he comes back up from the bottom again it's the cloudy background from Wildflower Fields. It could be used for the second screen in the ascent AND also keep the vertical bit from taking up too much space, know what'm sayin'.
Right, now picture this
(keep in mind that the scale here is NOT 1:1 by any means, these are just shitty little images to give you a general idea of the layout):
we have this first screen, down with the rest of, say, the "second floor" for this stage. There's an illusory wall hiding a diamond
(which no one actually cares about but is needed for authentic Wario feel), an archer, one of those "hit block to activate floor" walls blocking an intriguing vertical space, and a little wall next to the ladder (at the exact height that a dash jump can reach, as a courtesy to those speedrunner folk).
The archer is too high to aggro via jumping, but the platform is designed to be small, like 1/2 tiles wide. This is because somewhere in the room to the right of this one is one of the chef guys. The Fat Wario shockwave will knock the archer down from the otherwise unreachable platform, to be grabbed and re-positioned down below after visiting the nearby pools of water. These pools serve to de-Fat you faster, but also can kill your archer if you're a dipshit like me and try to toss the archer down too close to the water, where you risk either throwing it in directly or bumping it in with your fat ass because the ceiling's just barely too low to successfully maneuver around. The original Wario Land 4 is an asshole to you if you decide to be careless for puzzles like these, so why not emulate that. Anyway. The red block switch would be somewhere along the upper left-hand path.
Once you got hit by the archer, you'd then be free to ascend.
The next screen is, again, just a vertical chute, although it's a little wider than the entrance sets us up for.
Nice and rainy, uses jungle backgrounds still.
Then once you get past that it's like this, y'know.
Since we have a guy who knows how to replace textures on the team, all we'd have to do for the "clouds" to turn them into trees is a palette swap on the opaque, more solid-looking clouds (a la SMB1) in the immediate background.