The short version of my proposal for resting is a fatigue system based on average distance traveled per party member, and healing received from every source except short resting. You cannot long rest until after you have accumulated a certain amount of fatigue. If you exceed a high threshold of fatigue, you get a point of Exhaustion, and contining to exert yourself will increase your fatigue and exhaustion points until you reach 5, at which point you're forced into a long rest as soon as you're out of combat/conversation. Long rests remove all points of Exhaustion.
Balancing in this way is great, in an MMO, where everyone can affect everyone else. But "balance" in this scenario? Not seeing it as an issue, as I said, what George is doing over in Spain has no affect on me here in NA. Speaking of ignoring arguments, what about the argument that in higher difficulties, this feature may not work like it does here, in this one?
"But Rob, it's balanced this way in TT". Of course it is? In TT, there are other people affected by that one player that feels like they have to have a long rest after squashing a few rats. I ask this again, because this is the crux of a "balance" argument: How does whatever George is doing in whatever region adversely affecting you in whatever region you're in? House Rules for MP will cover this adequately, by disallowing it from the start, so that everyone knows it's not going to be a thing, and can base whether they stay in that party or not on that, if it's an issue for them.
This is not a case where "let players play how they want" applies, because it does effect overall game balance. D&D 5e is based on an attrition-based system where resources are depleted over time. It is not balanced around being fully healed and fully charged up for every encounter.
Given that we'll have a party of 4 which will be fixed at that size, that makes every party slot a precious resource which must be filled carefully.
Take the Warlock class. They get almost no spell slots, but they gain them all back after a short rest instead of a long one. In a system where you can only short rest once between long rests, but can long rest at will without limit, that makes Warlocks completely inferior in every way to Wizards. Wizards get a lot more spells known and a lot more spell slots and if they can use all their spells in every encounter and still be charged to fill for the next fight, that gives them no reason to hold back the power.
So yeah, before we start throwing out the bath water, let's be sure the baby's not still in the tub, and that there aren't different rules for this in higher difficulties, which are intended for those that are looking for a challenge.
If Larian has different rules for different difficulty levels in mind, then that needs to be communicated to the player. But based on the things they've said about how many different iterations of rule variations they went through even before EA, I'm pretty sure that Larian does not have any such rules firmly in mind yet. Until such time as Larian communicates on that topic, it's better not to assume there will be any such rules.