All these changes are defenetly idears, but how would it actually improve the game in a way not allready present?A zoo game simulator has so much potential for to provide deep gameplay. None of this is found in the Planet series.
Let's take the flamingo example. I think three species, Great Flamingo, American Flamingo, and Chilean Flamingo would provide the variety that's needed without becoming too repetitive. Each has a different native range, appearance, and most importantly different climate needs. These difference will dictate which species is best suited to each zoo.
1. Variety. Why do we need variety? Because flamingoes are a zoo staple and found in nearly every zoo. It is incredibly boring (not to mention unrealistic) to see the same species roster in every PZ player's zoo. Building an African savannah complex? Use the greater flamingo. Building a huge South American rainforest biodome? Use the American flamingo. Looking for the most vibrantly colored flamingo to add to your avian collection? American flamingo.
2. Location. Let's make the location that a player chooses for their zoo actually meaningful. Location dictates climate. Chilean flamingoes are far more common in more northern/temperate zoos because they are better adapted to cooler temperatures. That means they can be displayed outdoors in large, well-landscaped exhibits for a longer part of the year and have lower energy costs to maintain the species. When the climate is too extreme for a species it must be kept in indoor holding facilities. Indoor holding can be back-stage utilitarian facilities, or elaborate indoor display areas, such as a glass-enclosed aviary. Indoor spaces are more expensive to build and maintain (heating, cooling, ventilation, electricity, etc). Guests are unhappy when animals aren't on display.
3. Animal Market. Location also influences the animal market. Species are easier to obtain in the native range, and some species are much more prevalent in European vs. North American zoos due to historical reasons. These differences in availability would be reflected in the animal market. You can purchase any animal listed in the market but must pay a shipping fee based on how far that zoo is from yours. A small animal, like a flamingo, costs a lot less to ship than an elephant. The longer the shipping distance the higher the risk of disease or injury in transit. Greater Flamingoes are much more prevalent in Europe than North America.
4. Breeding. I don't know why flamingoes breed like sewer rats in zoo games. In reality flamingoes are challenging to breed in captivity. Flamingo flocks must reach a certain size, and have a relatively even sex ratio in order to breed. Some enrichment items, like mirrors, can help trick flamingoes into thinking the flock is larger and promote breeding. Other enrichment items, like pre-built nests, also encourage breeding. Adding a new animal or scenery to the enclosure, or moving the flock to a new exhibit can disrupt the entire breeding season. Even changing the keeper that cares for the flock can cause them to stop breeding - a good reason to retain your employees!
In the wild flamingoes nest in extremely inhospitable locations were there are no natural predators because ground nests are highly vulnerable to predation. In captivity both the eggs and parents are very vulnerable to predation while nesting. Flamingoes are also easily startled and can trample and destroy all the nests in the colony. Removing the eggs to a new staff facility, Incubation Centre, greatly increases the chance of those eggs surviving to hatching.
5. Guest Interaction. Guests love to interact with the animals; no longer is just viewing them in their habitat enough. Flamingoes can be presented on stage during a bird show, marched through the zoo along guest pathways at a scheduled time of day, or allow guests to feed them from pre-filled cups distributed by the keeper.
6. Diet. Giving the players a choice between different quality diets make sense. The player must find a balance between animal welfare and economics. Higher quality diet improves factors like animal happiness, health, and fertility. In flamingoes diet also has a visual impact. Flamingoes fed a low quality diet without high levels of carotenoids will loose their color.
7. Ethics. A new mechanic could be introduced. Flamingoes and many other large birds have traditionally been pinioned (wing partially amputated as hatchlings) to render them permanently flightless and allow them to be displayed in open-top enclosures.
Advantages of pinioning: open-top enclosures are much less expensive to build, especially for large enclosures; birds can easily be incorporated in mixed species exhibits with ungulates, open-top enclosures allow better sightlines for guests.
Disadvantages of pinioning: ethical concerns of permanently maiming birds, which can lead to animal right's activists protesting the zoo; decreased breeding efficiency; increased risk of birds being injured by trampling in mixed species exhibits.
Advantages of not pinioning: birds can fly, improved animal welfare, improved breeding.
Disadvantages of not pinioning (flighted birds): birds must be housed in completely enclosed exhibits, risk of birds escaping.
Imagine if this level of depth was added for multiple species. We might actually have an interesting simulator.
By all means keep sandbox for the sandbox players. I have always viewed sandbox as kind of a cheat mode for players who don't want to play by the game's rules. Sure sometimes its fun to just play around with the parts without having to worry about money or to test out ideas, but it gets boring quickly and then its nice to have actual gameplay to return to. If I just wanted to make pretty scenery I would do it in a 3D modelling program, like PurePolygons, that allows infinitely more design freedom than Planet ever could.
Besides the pinioning these changes are allready in the game like diet choices with so little impact that you put it in as a new point.
Planet zoo wont become a great zoo sim by many high effort tiny impact changes like those proposed here but by actual bigger sweaping changes that prioritise management like staff specilisation, better Energie management (Imput vs output instead of ugly forced builds) or introduction of management staples like ressource management.
Breeding requirements could be nice, but any big general change that doesnt need as much research would be much prefered