You Should Be Dead, But...
Save-or-die mechanics are pretty awful for straight-up challenges. I mean, you wouldn't exactly get a lot of tactical thrills from a game that boils down to "Flip a coin to see if you lose," would you? But that's not the only way they've been used.
Practices and opinions vary pretty widely in the OD&D/OSR community, but one way of looking at "save-or-die" is that the saving throw is the "second chance" mechanic.
Proponents of this approach say that falling into lava or getting stabbed through the chest ought to be lethal, so really the game is about avoiding those things altogether, not surviving them if they do come to pass. And the saving throw is there to decrease character death without removing the actual threat.
What this means in play and adventure design, though, is that you can't make save-or-die situations a thing that just happens to the PCs. Rather, you have to telegraph the threat and the PCs' main goal is avoiding it altogether.
For example, if the PCs are entering the lair of a gorgon ("medusa" in D&D terms), they'll know it from the crazy-looking 'statues' all around. The challenge is sneaking past the gorgon, or fighting her without looking at her (probably using a trick of some sort), or even negotiating with the clever and cunning monster for safe passage. If they're having to roll saves to avoid petrification at all, it means they're screwed up the actual plan badly.
Unfortunately, this approach doesn't really work if you want an adventure to involve a series of challenges the PCs are mostly expected to face head-on — because that's your idea of heroism in the story, because you want to play some thrilling tactical battles, &c. What happens then is the players will be rolling those saves not as a failure consequence but as a result of engaging the scenario at all, and of course some will fail and die kinda out of nowhere. That's one of the reasons 4th Edition D&D in particular removed the "save-or-die" angle from the game.
Adding More Second Chances
So, you don't want characters to die all the time, but you want them to feel like their lives are constantly at risk (which is a bit of a contradiction, yes, and it's good to recognize that).
Well, if you want to maintain the "threat" of death, I recommend trying to lessen its occurrence, not its impact. Dependable resurrection mechanics essentially redefine "death" to "XP/loot penalty" or "sidequest" (it's worth noting that some older D&D editions had "system shock" rolls to keep resurrection from being a sure thing). If you want death to be scary, I think it should have some finality to it. Focus on giving players a way to narrowly cheat death rather than a way to straight-up undo it.
One way to do it is to bolt on an explicit death-cheating mechanic. Some established patterns include:
One approach that feels rather "old-school" is the "death and dismemberment" table. Make a random chart of nasty things that happen to you. Death is on there. So is other stuff, though. The idea is to replace death with "a chance of death or maybe you just get screwed up some other way." Here's an example with a variety of brutal but non-lethal outcomes.
Many games try to balance gritty combat with survivable heroes using limited metagame currency for avoiding failure consequences, in the style of WFRP's Fate Points. If you can straight-up rewrite the outcome with a point, then they're kinda like 'extra lives.' If you want to make it less of a sure thing, have the points give you a reroll instead.
I recommend using a pure metagame resource instead of something in the fiction (like resurrection scrolls or whatever) because I think creating fictional elements that allow you to defy death necessarily draws a lot of attention to those elements, and invite the PCs to go messing about trying to figure out how to 'game' the system (e.g. score more resurrection scrolls so they can't run out).
Save-Or-Die and Converting Between Editions
Another thing to note is that the different D&Ds have different save mechanics.
- OD&D and AD&D (and many OSR games, likely) have a chart with fixed saving throw numbers. Most effects just trigger a save on the chart. This means that, as you level, you'll consistently get better at actually making those saves.
- D&D3 and D&D4 (and most other D20 games) have rising modifiers, but you're rolling against DCs that scale with the level of the challenge. Thus, characters can end up falling behind in their saves (especially any "weak" ones) as they level.
Be mindful of this when converting: mid-level characters in OD&D or an OSR game might actually be way, way better at making their saves than equivalent characters in a D20 game.
No, that sounds fun and flavourful. I'm picturing Vikings at the moment because it fits really well, but it would be a neat detail for all kinds of made-up cultures.
There will be published adventures that will go contrary to these expectations, and you'll either have to not use them or spend time adjusting them to fit into your setting better.
The big caveat is that there are player types that this would bring either no positive to the game or actually be a negative. Players who are there to mostly roll dice, have fun with their friends, and unwind without having to really think hard (a totally valid reason to play RPGs) won't work well with this, since that play style relies on using more standard RPG tropes and not thinking too hard about them or the setting's internal consistency. If you have a group like this, or even one player like this, running a game like that will introduce more or less significant friction that you'll have to deal with somehow. (Usually, friction means changing what you're doing, or changing who you're playing with. Sometimes the players adapt, but players are less likely to invest the energy to adapt and that's especially true of the roll-dice-and-unwind type of player.)
A lesser caveat is that you will have to think about how this interacts with the D&D spells that can bring people back to life. Is that an offense against the gods too? Or does properly burying the body permanently ensure the spirit's place in the afterlife and you can't bring them back (and those spells don't work)? If this bit of metaphysics interferes with the (somewhat) common trope of D&D being a game where dying is just an inconvenience, then that will require some adjustments too, either to adventures' difficulty or to your players' expectations, as above. On the plus side, if you and your group are sick of death being merely a speed bump (and enough people do dislike that side effect of D&D's standard spells), then that's a feature! It would be for me.
So long as you have a compatible group and you lay this out up-front – which you should do anyway if this is a major part of the players' characters' culture – this should be fine. Adding a reasonable explanation for where ghosts and ghouls come from is the kind of setting design that a lot of players appreciate. In this particular setup, the players may also come to appreciate that it means their enemies will be reluctant to kill them out of hand, too.
As for wealth considerations, in D&D Next you won't have trouble with wealth. Unlike its two predecessors, it doesn't make wealth required for them to meet an expected power level for their character level, because it has mostly done away with the concept of expected power level. (At least, not as part of the "core" D&D Next rules. Stuff similar to 3e's Wealth By Level or 4e's treasure parcels will probably show up in the modular optional rules.) Your suggestions for how to place "adequate" treasure seem eminently reasonable, where "adequate" in a system that doesn't super-care about wealth is defined by how much treasure you think should be coming the PCs' way in a given span of time.
Best Answer
It depends on which spell you use to bring back the dead.
There are five different spells that you can use to bring a dead person back to life, and they all work a bit differently, as you might expect.
Raise Dead
From the spell description:
Reincarnate
Reincarnation completely replaces your body, so it will cure anything that ails you. Of course, it has the downside of not knowing what kind of race you'll get.
Revivify
Revivify doesn't explicitly say anything about what it does or does not cure, but seeing as how it's a low-level version of Raise Dead, it seems pretty clear that it's not meant to cure anything, magical or mundane. So if you died of poison, you'll still be poisoned when you're brought back with 1 hit point.
Resurrection
From the spell description:
True Resurrection
From the spell description:
Conclusion
Extrapolating from this, it seems fairly clear that the assumption is that, unless otherwise stated, conditions are not removed when you die, or when you come back to life.
For the specific example of exhaustion, none of the spells directly call them out, but it seems fair to lump them in with "poisons and non-magical diseases", so anything other than Revivify should cure it. Note that this interpretation does mean that Revivify can't be used to revive someone who died of exhaustion, since they'll come back to life with 6 levels of exhaustion and immediately die again, but this isn't necessarily a bad thing.