Other RPGs don't have this because they are afraid they will alienate the casual player. Well, given how popular the 'hardcoe' mode in FO:NV was, I think gamesas can take a risk. Players will learn that their character cannot always be 100% perfect and unscathed.
ITEMS ITEMS ITEMS
Not every person should have a Pip-Boy. There should be separate items that characters need to watch out for themselves. Instead of having a free HUD that gives all the info you need, maybe the HUD should be filled with info based on what the character has in their possession.
Do you have a Geiger counter? Good, then you will not walk into radioactive areas without knowing it and get yourself burned.
Do you have a compass? Good, then the typical N-S-W-E directions will be added to your HUD.
Do you have some fancy-schmancy sonar-tracker device? Good, then you will have a short-range radar screen in the corner of your HUD.
And these items will create a demand for the items to be looted, crafted, and bartered. (The need for demand is a recurring theme in my ideas.)
FOOD/WATER DEBATE
Characters should become dehydrated, tired, hungry (Not as quickly in a real-time sense as NV). This will increase the need for the players to do the following things:
1) Plan ahead. This is not some stroll across the plains to get easy-to-find loot. Each mission, journey, needs to be an expedition. At the very least the player needs to have some basic provisions on them.
2) It will create a demand for basic goods that players can sell to make profit, whether they be looted (Salisbury Steak) or crafted (Radscorpion Tacos). Some games that had a food-crafting skill set, just had it all go to waste because NOBODY bought the items unless they were really high-level buffs after days and days of meaningless grinding.
3) It might even create objectives for player-originated PvP conflict--such as control of a water resource etc.
MEDICAL PROFESSIONALISM
Healing in most video games, online or not, is usually freaking LAME. The healer character pushes a button or a magical salve is used. Though obviously Stimpaks are needed for continuity and playability, I think some serious effort should be put into the medical skills of the game.
Instead of it just being a magical ability at the push of a button--it needs to be a mini-game in essence. Though characters can help themselves to a basic Hit-Point replenishment degree with a stimpak many times, there needs to be inflictions that only a character with medical skills can address, such as broken bones, poisoning, organ injury, radiation burns, etc.
The character filling the role of the healer needs to have such tasks before them that are more interesting, challenging, and rewarding than "Push J to heal the character and get 50XP points!!!!". For example, there could be a Pip-boy like menu in which the medical character inspects his ally for advanced damage or afflictions (Maybe lower skilled medics can have difficulty identifying certain problems). Then they must use their limited supplies to prioritize and address the problem. Maybe the afflicted player can have symptoms--random barf animations, bouts of dizziness, etc that can actually be used to DIAGNOSE a problem. If the character is barfing--he could have been poisoned OR he could have radiation sickness.
And if these supplies to help are made from items that are uncommon--then BAM--we've created more instant demand that can be used to reward the player for their time.