This is my idea to improve survival techniques, using plants and cooking system:

Plant A: Helps you to combat infections

Plant B: Sedative effects, help to fight pain. If a lot is taken, you could get unconscious.

Plant C: Poisonous plant, can cause blurred vision, vomits, or depending of the amount can cause a heart attack.

Plant D: Maximize the effect or other plant.

To craft a usable solution, you are going to need:

-Gas canister + Portable Gas Stove, to warm up the mix.

-A container, like a laboratory flask or a cooking pot.

A little bit of water, if a lot is dropped, you could minimize the effect of the mix.

Possibles mixtures:

Water + plant A + plant A+ plant A: heavy anti infections effect.

A lot of water + plant A: diluted mix, no effect.

Water + plant A + plant B: antiinfective and sedative effect.

Water + Plant A + Plant D = heavy anti infections effect.

Water + Plant A + Plant B + Plant D= strong multiple effects, could kill you.

To simplify mechanics, you would only be able to mix 3 kind of plants, or ingredients, whatever you want to call it.

How to apply:

Syringe should be the logic way to apply the solutions to yourself, but could be other ways:

Darts: Chris Torchia, the Art-Lead of DayZ asked for experiences about dart guns. The posibility to craft a solution for dart and cause a specific effect in the target could be quite interesting, and would add complexity to the survival gameplay.

Hollow arrowhead: Due to the disadvantage of using a bow against firearms, hollow arrowhead with a mix of sedavite/poisoned could balance the combat making the bow a more dangerous weapon, and it also adds a great survival atmosphere.

How to learn about this: There could be a book called "survivalist for dumbs", that could contain information about how to make the mixes, talking about proportions or plant and water, or other liquids used to create the mix.