Man, I was JUST thinking of posting something like this. You guys have already read my mind on some of these. And this is for all future "Planet" games, not just PZ2.
The biggest things for me are:
How paths work.
We all know it's insane how much you have to fight with the pathing system sometimes. I'm sure I don't have to go into detail, because both the users and developers just know.
I understand it must have been hard figuring out a system that controls were the guests can go, that doesn't clash with where the animals can go, or freedom of placing construction pieces, etc. So they have my understanding. But...
There's gotta be a better way, man.
How the construction pieces, rocks, paths (ect?) work.
So like I said, I appreciate what they have going, as of this game.
But in retrospect
for the love of god
why can't we just select a piece, like the simple 4x4m wall, or Large Rock 2 or whatever, and then change it's texture to one of the other themes or biomes?
I'm sure the developers were kicking themselves when they realized this. Like, having a listing of the exact same rock models, but then in different textures for each biome, just clutters the UI. Same with the different construction themes that have the exact same pieces. You could just have a list of pieces and then select to change their themes. I know there's some pieces that are unique to certain themes (like the castle tops in the twilight theme) but that's ok if those ones only have one theme option.
Same with the paths. Could you imaging being able to highlight a section of path, then just change it to another path-type, instead of deleting and rebuilding it all? Same with not having to delete and rebuild whole sections of buildings or rockwork if you realize you want a different texture or colour. And it's a shame the trend of almost everything being flexicolour wasn't here from the start. Everything should be flexicolour.
!!!! edit, because I forgot construction piece grouping. Not being able to group a bunch of pieces, because it turns out more than one of those pieces is a "construction" piece, is so frustrating. There should probably be a rework of how "groups" work in the next game. Also a safeguard against accidentally deleting a bunch of stuff, because you didn't realize it was grouped with something else!
Make it easier to select the piece you want when there's a bunch of pieces near each other.
That's it, that's the tweet. There's got to be a better way. This one's probably the biggest bane of all us builders.
Bigger and better terrain tools
Same.
Better-looking guests
PLEASE. I understand why they wanted to just import the guests from Planet Coaster. But for any future Planet games, they've got to redesign them. They don't have to be as realistic as the animals (in fact, too-realistic humans can be very uncanny and creepy in a game like this) but at least more realistic than the current ones. And less distracting.
Better transport vehicles
The giant space gondola isn't real, it can't hurt you
How concession stands work
Others have mentioned already that importing the concession stands from Planet Coaster just.... didn't really work for a zoo game. And some of it was already weird in Planet Coaster.
Theme parks will have the occasional stand that's just for popcorn, or giant roasted turkey legs, or deep fried oreos or whatever. But for a zoo that's much rarer. Food isn't as much of a draw. And a zoo needing concessions EVERYWHERE to satisfy guests makes no sense.
And it's just odd not to have options like "simple grill concession" (sells burgers, fries, and drinks) or "small refreshment stand" (just sells drinks and frozen deserts.) Only having individual foods/drinks and then one big "restaurant" option seems to be a holdover from older games. And it's strange that Frontier copied this method just because "that's the way management games always did it in the past." We need to break this curse.
How time (and guest/animal need depletion) works
I think you can't really separate these. There's an option that lets us slow down animal aging, which helps. But I think we need more control across the board. How fast things dilapidate and break down is also a big factor. You never want a game like this to feel TOO rushed and frantic, even if you're playing a challenge mode. And I know they had less to balance, but Zoo Tycoon 1 and 2 better captured the speed of a zoo progressing, and matched challenges to this instead of actual real time.
User control over what the terrain of your park and the terrain around it looks like
I think this might just manifest as more interesting options for park maps. It's cool to have height maps. But just wanting a city in the background, or one that flows seamlessly into your map, would be great for immersion. PZ is at least much better at this than Zoo Tycoon 2 was, and it seems to have taken notes from Zoo Tycoon 1 and Roller Coaster Tycoon 1. But it could be better!
A setting for how active animals are
Being able, at least in sandbox, to scale back how active animals are-- lowest being "realistic" (a lot of sleeping, foraging, and grazing) and the highest option being for kids who want their animals to be constantly entertaining them. Our zoos would look so much better without the animals running around like aimless robots. I think if you implemented this, players would wonder how we ever lived without it. Could also be used in other Planet titles to control how guests function.
Optimization and Progression
Others have already elaborated on this, and I just rambled about progress in that other post. But yeah, I agree.