Do people not want resource management???
Nes. Yo. Naybe.
It's sort of like inventory tetris. The
idea of having to carefully manage your inventory so you can maximize your usage of it sounds great. In practice, unfortunately, it's mostly tedious and frustrating. Resource management often hits the same notes: the idea seems cool, but in practice it generally feels like you managed resources
in order to avoid being punished, rather than managing resources
so you could do well.
And that's sort of the crux of a lot of mechanics like this (spell components, for example, are in a similar boat in most games, though I hear Torchbearer actually uses them extremely well.) Making them have teeth almost always makes them feel like doing chores so you can avoid bad things, which sucks the fun out of participating. Most other proposed "fixes" for powerful casters, such as spell failure chance or a constant risk of magic blowing up and doing bad things (sometimes
very bad things) very frequently cashes out as "jump through hoops to avoid suffering" rather than "rise to this fun challenge in order to be awesome!"
But as a DM, I do, especially because I want to be able to challenge my players without resorting to high CR monsters that are less narratively appropriate.
Then, IMO, you are barking up the wrong tree entirely. You challenge your players by presenting them with situations where they cannot
calculate a clear correct action, and must instead make difficult value judgments. Changing the rest mechanics simply alters one of the variables in the calculation, rather than making it so calculation is not useful. And, as part of that change, you run rather a great risk of teaching your players to avoid taking risks and avoid engaging in adventures that involve time pressure, because they are (by definition) rewarded with greater chances of success when they avoid such pressures.
I don't like it, its obviously nerfing the players, and players dont like nerfs. Plus, most people have trouble remembering too many house rules.
A better way to do it is be more liberal with giving out Exhaustion levels. Long distance travel at fast pace? Exhaustion. Lack of food/water? Exhaustion. Long rest in poor conditions? Exhaustion. This monster over here? Has an ability that gives you Exhaustion.
Once the PCs have more than 1 stack of Exhaustion, it takes multiple Long Rests to get rid, but they can still try to power through stuff if they feel confident, or simply dont mind the risk.
....Exhaustion is
so much worse than the proposed house rule, I'm...genuinely shocked anyone would think it was a better alternative.
One level of exhaustion essentially makes combat a non-starter. Two doubles down on that (speed halved), and three makes doing
literally anything suck (because you have universal disadvantage). Being liberal with Exhaustion is basically just nerfing everyone in highly randomized ways, and forcing them to rest
even more often than the proposed house rule.
Exhaustion as written in 5e is
even more a "neat idea, dull/anti-fun execution" than resource management normally ends up. There's an extremely good reason 5e doesn't use the exhaustion rules very much; they suck and are really, really not fun.