I also tend to err on the side of grim & gritty in my campaigns, although I don't like the Gritty Realism variant. Requiring long rests to be 7 days slows down play and isn't fun. But that's another discussion entirely.
Anyway, I have also sought to factor environmental conditions more prominently, especially with respect to resting in the wilderness. I don't want resting to take a week but I also don't want to it to be
easy.
Here is the start of a system I've been working on:
Environmental Condition | Hit Points | Hit Dice | Exhaustion | Spell Slots | Disease Recovery | Contract Ailment | Death Saves |
Good | All | 1/2 | 2 | All | Normal | No | 1 |
Average | All | 1/2 | 1 | All | Normal | No | 1 |
Poor | 1/2 Max | 1/2 | 0 | -1 | Disadvantage | DC 5 | 0 |
Harsh | 1/4 Max | 1/4 | 0 | -2 | Disadvantage | DC 10 | 0 |
Hazardous | Can't Rest | | | | | | |
Average is the baseline. It means generally favorable conditions relative to the campaign setting (the baseline for the Sword Coast is going to be different than Dark Sun, for example) and assumes that the PCs have adequate camping equipment, a supply of food and water, the area is safe and protected, etc.
My system also includes options for reduced hit point, hit die, and spell slot recovery, penalties to recovering from a disease and even the chance to possibly contract a disease. These are all DM options of course.
This is all to incentivize the group to plan ahead, make sure they have the proper equipment, and enforce consequences when they push ahead. It also introduces lots of design space to further flesh out the travel activities on pg. 183 of the PHB, increase the role of the ranger, expand the use of the Survival skill (and other skills), etc.
At the DM's discretion, they can adjust the conditions up or down 1 category if the group is unprepared. Even if the weather is comfortable, camping for the night with only the clothes on your back isn't going to result in a restful night's sleep. Conversely, poor conditions (like below freezing) can be upgraded if the group is prepared: cold weather clothing, a tent or shelter, warm fire, etc.
This system also provides a "reward" for smart play: the ability to regain exhaustion more quickly. So the group can choose to push ahead when they know they are prepared and can find safe shelter during their journey.
This system is a subset of a larger system that also adds mechanics to the Lifestyle conditions:
Lifestyle | Hit Points | Hit Dice | Exhaustion | Spell Slots | Disease Recovery | Contract Ailment | Death Saves |
Aristocratic | All | All | 2 | All | Advantage | No | 2 |
Wealthy | All | 3/4 | 2 | All | Advantage | No | 2 |
Comfortable | All | 1/2 | 2 | All | Normal | No | 1 |
Modest | All | 1/2 | 1 | All | Normal | No | 1 |
Poor | 1/2 Max | 1/2 | 1 | All | Disadvantage | DC 5 | 1 |
Squalid | 1/3 Max | 1/4 | 0 | Lose 1 | Disadvantage | DC 10 | 0 |
Wretched | 1/4 Max | 0 | 0 | Lose 2 | No | DC 15 | 0 |
Same rules as above apply, although the range is expanded. This also assumes an "urban" environment, which again, is going to be relative to the campaign world.
Note: This system could also include rules for the Lingering Injuries variant in the DMG, such as easier or more difficult recovery.