I think in terms of water, food, temperature, wetness, shelter, energy/stamina, and distance from civilization.
An (optional) prolonged start where you were started a long way from civilization with no supplies represents a survival start. Starting within a few kilometers of a settlement is not survival because the remnants of civilization will provide shelter, tools, and resources. So, for a survival start, I think you have to cross a wilderness map to get to the main map. For a non-survival start, you start on the main map as you do today. The survival start's map is a desert that doesn't have water. You might be able to hunt rabbits for food. The survival start's map doesn't have any POIs, just rough terrain. The goal is to get off the survival map. This may not be popular because it is a walking simulator, but it is a survival start and I think it mimics a classic A16 start.
Once you reach the main map (built as RWG makes them today) then you're likely hurting and I think the game's current food/water work. Starting in the Forest will leave temperature out of it and while rain might make you wet, since the temperature isn't extreme you're okay.
I think you should never escape the possibility of dysentery. Murky water would have a greater chance. Boiled water would still have a (smaller) chance. The teas would have a tiny chance. The helmet filter mod would reduce the chance. And, when you get it, Chrys Tea only partially clears it. The only way to eliminate dysentery would be to take Iron Gut. You can put the eventual progression into bloody dysentery in and lead to death if you want.
Temperature fits into the desert and snow biomes. Put some variation of the A16 extreme effect into play, but they don't have to be quick onset things. Heat Stroke and eventual death to Heat Stroke are okay. I forget what the snow versions are. When a storm is happening, make those nasty temperature things onset quicker. Wetness can cool in the desert, but should really hurt in the snow.
For the wasteland, let the temperature swing from desert heat through snow cold, but also add an element of unspecified toxicity. That is, don't commit to it being radiation. You can have the desert storms, snow storms (without accumulation), or a toxic storm. I don't know what a toxic storm should do. If you want to get nasty, have it slowly decrease your max health and stamina. Maybe shelter doesn't stop a toxic storm.
Yeh, I don't have any hopes of being close to what gets done.
