Here is my idea, it is my take on the best idea I heard. This is essentially a combination of the OP's 3 and 5 ideas.
Th game would have some sort of hidden fatigue meter, which increases based on the average number of steps the party has taken since the last long rest, and also increases when receiving any sort of healing EXCEPT that from Short Rests (because the idea is to encourage more short rests, and spacing out long rests. And also forcing a long rest right after a short one because the short rest healing kicked you into high fatigue seems silly). You would not be allowed to long rest until a certain amount has been passed. Let's say 67% of the way to a point of Exhaustion. Once the fatigue meter has passed the mark, it becomes visible, and if you continue to neglect it for, say another 25-33% past the fatigue point, the party will get a level of Exhaustion - much like how pressing forward without long rests in 5e will make the party take one as well.
Continuing to neglect Exhaustion more will eventually cross a second threshold and reduce movement speed by half. This might not necessarily grant a second point of exhaustion immediately, as that should be enough of a clue to players "you should really rest right now". But if they keep going...
If you cross an Exhaustion threshold in combat, it won't take effect until the combat ends, then take effect immediately.
The tricky part is figuring out how many steps and how much healing it should require to reach those levels.
1. The average number of steps would be the combination of all the steps taken by everyone you've had in the party since the last long rest, and divided by 4. So if you're all traveling together, everyone will have about the same. If you have one person scouting ahead and sneaking and moving, they'll do more than other people, but if they do an extreme amount of sneaking, it'll eventually average out.
2. Healing which takes your hit points past maximum doesn't count the overflow towards the fatigue meter. Short rests also do not count towards the fatigue meter.
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This is better than a method based around consuming resources to long rest, because it prevents you from being blocked for lack of resources - you can walk around some more. You also can't stock up on resources to trivialize long rests.
This is better than a random encounter system because if you're really on your last legs and NEED the long rest, you won't be attacked at your weakest. (Or you won't need to long rest immediately after a long rest because the random encounter went badly for you.)
Th game would have some sort of hidden fatigue meter, which increases based on the average number of steps the party has taken since the last long rest, and also increases when receiving any sort of healing. You would not be allowed to long rest until a certain amount has been passed. Once the fatigue meter has passed the mark, it becomes visible, and if you continue to neglect it for, say another 25-33% past the fatigue point, the party will get a level of Exhaustion - much like how pressing forward without long rests in 5e will make the party take one as well.
Could work, but there can be a few problems:
- Do you count movement in combat? Because then all melee parties will get exhausted faster than all ranged. If you have a balanced party then might not be an issue, but something to keep in mind.
- Movement in civilized areas can cause a lot of exhaustion even though you don't use a lot of combat resources - exclude those areas?
- Fast travel - although this can easily be solved by adding an amount of steps, based on distance
- Jumps? Although I hope they tie them to movement, so shouldn't be an issue if that is done.
Good thoughts. Let me think...
1) Let's say "out of combat".
2) I'd say include. Walking around all day can be tiring as well. In my mind I imagine that healing would probably be notably more exhausting than walking.
3) Fast Travel... Maybe, or maybe not. If it were to count, perhaps at least a 50% discount on the amount of steps it would take. Calculating a step count if Fast Travel is activated in the middle of nowhere could be tricky, though.
4) Jump is movement.
