What would solve alot of problems (maybe even the broken food cost mechanic no one seems to care about) would be if the food system would be overworked.
Don't let food spoil, don't let keepers be overpicky what they fill with food.
The game can't handle its own system.
I saved my secondary zoo by cutting personal and accepting that guests complain (they destroy everything anyway), but i still
have food costs of 50k in one year and 90k next year, then back to 60k, up to 85k without changing the amount or type of animals.
That can ONLY happen when
- food spoils before its eaten (in crazy amounts)
- food is put to devices animals can't reach it (and then spoils)
- too much food is given out (and then spoils)
- animals have broken eating mechanics
in other words, it can "only" happen when thousand little things go wrong.
The game can't handle the realistic approach of animal food it tries to achieve.
Cost per feed, accurate calculation of the amount of food that is needed, spoilage times for food.
It... does... not... work.
Otherwise you wouldn't get complete hillarious jumps in one of the both major costsources of the game.
To let loose on food restrictions, like double the amount that is given out and get rid of spoilage (or drastically change the time of it),
would solve several problems at once.