Ok sorry about the length, I'm speaking 11 years of "sequel wishes" here!

A highlight of my main park is how much of it is underground. But man is this a hassle to maintain. Where to start...

Janitors. I like the realism idea of janitors, but if you have 2 or 3 paths, all going along the same gridline but at different heights, if you try to put a janitor on one, he'll think he's in charge of all 3, meaning if someone throws up on the top path, he'll walk around the entire park to get to the top floor to clean up one vomit, then all the way around again. This adds up, next thing you know guest numbers drop and vomit and litter is at -140+ and you can't get your janitor to stay in one area. Hiring more just makes it worse. I've had to close my parks down and wait for 6000 people to leave, just so I can have the janitors walk around for 45 minutes finding all the vomit.

"Selective" invisible scenery and height placement. I have an underground water section in my main park. Basically the terrain is lowered all the way and I built the water park down there. Unfortunately it's impossible to make it actually underground so I had to use scenery blocks to make a sort of "ceiling." Not only was it near impossible to hold shift and raise the pieces high enough before I reached the end of the screen (meaning I couldn't get it high enough without extreme difficulty, had to develop my own workaround), when I finally DID finish it, it was a hassle to make changes beneath it. If only I had a way to just turn those ceiling blocks invisible but not all scenery, would've been sooooo much easier.

Camera controls. When inside a pit or against a mountain, if you back up too far and hit the wall, the camera jumps all the way up on top of the wall. When you have to move the camera in marginal increments at a time and you're trying to find that sweet spot to see while you build, right when you hit it the camera jumps up and you have to start over. Maybe have a slight pause before the jump so you can back up against a wall first. Keep holding back THEN it will go up. Just another thing that would've made designing these underground sections so much easier.

Last thing, roller coasters. I KNOW this has been mentioned, but the blocky look of underground coasters is just tragic. This must be changed, and I'm sure it already has. Though another thing would be the track lights. They can be so bright that while testing it out you're blinded and it's difficult to see anything at all, particularly with white lights.

This is all that comes to mind right now. If anything else comes up I'll report back here. So excited!