OK, so you are addressing several different things in these posts. But to start with, I totally disagree that different stories require different resting frequencies.
They require different pacing. If a story plays out over years, you can't play through 6-8 encounters every single day, everyone will be 20th level (or dead) long before the climax. If you're running the fantasy version of 24, you might have 30 encounters in a single 'day.' You might sack out every night in the years-long story, or not slip a wink in the 24 story, so you're not changing rest frequency (much), it's the pacing of how much /action/ there is between any two rests that varies.
The
game 'requires' the same resting frequency: 6-8 encounters/2-3 short rest/ long rest. (And it's not a requirement, more a warning label.
WARNING: if you think balance is a joke now, wait until you run a series of single-encounter days, you poor sucker.
WARNING: do not exceed recommended dosage of 6-8 encounters per day. Larger quantities may be toxic to your campaign, symptoms may include character death, loss of friendships, or edition warring.)
the rules for resting certainly shouldn't change from adventure to adventure. You've decided that they don't get to rest in the desert - not because of any meaningful aspect of the fiction, you just don't like it.
It's a desert! That's not just a meaningful aspect of the fiction, it's the defining aspect of a trek through the desert.
But that first encounter ended up being much more deadly than you expected because of some bad tactics and bad die rolls. Now what? You've changed the rules and said they can't rest at all. Not a good solution. Something like the rules for resting should be consistent.
Don't see how that helps. Whether the party's first encounter goes horribly wrong with the next oasis is 3 days away, or when the princes dies in half an hour, you've screwed up. Better to keep an eye on things and not let encounters go that horribly wrong, in the first place.
Sure they can be killed, but it's not likely. You want an edition that acknowledges that the resting mechanic is a "problem" - I think it already does that.
It does, that's why it gives you the 6-8 encounter guideline. Because it doesn't work as well the further you stray from that, it's up to you how to cope. You can apply time pressure until it seems absurd, you can throw in wandering monsters until the PCs are ready to tell them 'take a number,' you can adjust the difficulty of encounters to always be much higher when there's more encounters and much easier when there are many, you can arbitrarily over-emphasize the short-rest PC's particular at-will abilities when there aren't enough short rests, or the long-rest characters' when there aren't enough of those. You can give the PC with no long-rest recharges a magic item with some nice 'daily' special abilities so he can nova along with everyone else in your 1 encounter/day campaign.
That's exactly why the DMG has alternative options - because they're acknowledging that the default design isn't for everybody. You just don't like any of their solutions.
The alternate options are OK, if instead of wanting to generally pace your campaign around 6-8 encounter days, you'd rather pace them around 6-8 encounter weeks or something just as consistently. If you want more flexibility in pacing, they don't work, even swapping among them may not work that well. Giving yourself the same level of flexibility by freely ruling rather resting is possible and how long it takes in each given situation, OTOH, can work.
This is an inherent problem with this type of design.
It is, yes. The 'type of design' being resources that recharge at different intervals and in different quantities for different classes, rendering class balance and encounter balance heavily dependent on a narrow range of pacing.
It's not easy to fix after-market, you'd have to re-design most of the classes, for instance. It's not hard to avoid designing into a game in the first place. Either don't use recharge mechanics, or dole them out fairly evenly. 5e chose to design-in this inherent problem because D&D has always had it to some extent (even in 4e while class balance was robust to changes in pacing, encounter balance could be distorted by a very short 'day'), and a game without the issue wouldn't feel like D&D.