Returning to the OP:
If your players want to try the house-rule in the video, here are some thoughts that would help go with it.
When we adopted a level of exhaustion a 0 hp, we adjusted lesser restoration, allowing it to remove a level of exhaustion but ONLY the first and second levels. You could upcast it to affect higher levels of exhaustion. For example, if a PC has 3 levels of exhaustion, lesser restoration cast with a 3rd-level slot would remove that one level.
Another house-rule is Endurance: you ignore the effects of exhaustion up to a level equal to your Constitution modifier.
For example, if you have CON 15, the first two levels of exhaustion to not affect you, however once you have a 3rd level of exhaustion, all the effects are there.
A general house-rule we use for upcasting is Maximal Upcasting: when you upcast a spell and gain additional dice, those dice are considered to be maximum and you do not roll them.
So, the cleric with Wisdom 18 upcasts cure wounds
using a 3rd-level slot. Instead of 3d8+4 you would get 1d8+4+16 (the max of the additional 2d8s). This gives you an average of 24.5 instead of 17.5.
We do this for all
spells, so it has other impact of course, but it is one of our "Golden House-Rules".
FWIW, I don't run my game with the 6-8 encounters adventuring day, but play with the adventures completely organic. Sometimes the PCs might have just 1 encounter (or none LOL) and other times they might have a dozen! It just depends on what they are doing...
Any way, with the house-rules we've used, the effects of the added levels of exhaustion are mitigated quite a bit, BUT THEY ARE STILL THERE, which does still increase the over all sense of danger.
Now, concerning the end states of combat. Myself and others have proposed different end states that are possible. I'm not sure exactly what you're looking for with that. However, if you want to continue discussing that aspect, please let me know.
Otherwise, as I began, if your players are interested in adopting the video's suggestion, it might help to consider the above house-rules we've been using for well over a year now (well... maximal upcasting might be a bit shy of a year...).
Thank you, but the fact of the matter is, I'm pretty sure they'd hate the exhaustion penalties if they were implemented. Changing lesser restoration
to remove fatigue like it does in Pathfinder (and possibly 3.5 too, it's been awhile) would just force the Cleric to use more resources than they already do. Personally, I don't actually believe my players are happy with 5e, but they are stubbornly resistant to changing games at the moment. I'm trying to use minimal house rules as well, because I noticed a trend- in the past, I would have large lists of house rules, and all that happened was, the players always forgot them!
It was too much to learn the game and then relearn the game. It doesn't help that no two tables play the same way, and if they see a video on youtube or tiktok talking about the rules, they come back to me and say "this is supposed to be like this, why would you change it, that just confuses me!".
So I'm like, fine, you want to play by core, we'll play by core. Most of the adjustments I've done are behind the scenes stuff they don't see, like adjusting monsters or changing magic items- for example, I've all but done away with attunement.
They still only have 3 attunement slots, because that's what they are used to, but items only have attunements if attuning to the item unlocks an additional benefit. I got the idea from a cursed axe in the update to Hidden Shrine of Tamoachan- if you attune to it, it gives you 5 extra hit points.
I also have magician's guilds who can create more "generic" and all around useful magic items if commissioned to do so, to ensure that anyone can get magic weapons, armor, and stuff that I feel is needed, but not game breaking, especially utility items that normal wealthy people would want.
The cool stuff is saved for adventuring.
IMO, magic items are the best patch for many of the game's woes, if you don't want to extensively overhaul it's engine to the point it's unrecognizable to the average player. I've been playing for a long time, and I've long since weaned myself of any reason for D&D to abide by real world logic. You took massive damage and are fine the next day? That's why it's called fantasy
I mean, you don't read a story where Conan hangs out in an Inn for three weeks recuperating very often, do you? What, he was beat up, dragged out into a desert and left to die? Well then, he gets up, murders something with his bare hands for food, drinks it's blood for water, walks out of that desert, and murders the guys who beat him up in the first place, then takes their gold and uses it on ale and women! That's how Cimmerians recuperate!
If they want to describe their characters limping around after a massive battle, that's cool with me. But I don't need to penalize them more because a fight was rougher than anticipated. The extra resources they'll have to use seems punishment enough to me. If they want the game to be more hardcore, I can just use tougher encounters.
And I just got a message from one of my players who saw my post with the old school critical hit chart and wants to use it in the game. These guys... shakes my head