- Spell system: it's really the worst. Having to take a long rest to regenerate spells is meaningless and tedious. Nothing prevents me from doing it after each fight so what's the point? Either implement some kind of meaningful constraint on taking long rests or just remove this tedious mechanics altogether, it's just a waste of time at the moment.
I would say DnD has far richer spell design. But yeah, per-rest casting never quite fits cRPG stucture. That was the case, and a problem with BG1&2. Recent cRPGs either ditched it, or tried to limit it somehow. I doesn't seem like Larian has any plans to address it in any way.
Restrictions on long rests are among the most important things required for BG3. High level spellcasters resting after every encounter will lead to an even bigger balance problem that doesn't have good solutions. Even if the classes would somehow be balanced with unlimited long rests, it wouldn't deal with the fact that resting after every encounter is just an incredibly tedious mechanic.
Easiest way to discourage carefree long rest spam would be to put a gold price tag on them. Camping supplies. Then the game would reward you in gold for playing well and using your resources with care.
I'd also like to see local resting spots and a redesigned fast travel system with waypoints to reach those places quickly if you have to backtrack.
(The silly teleportation runes should be turned into waypoints for mundane fast travel by foot anyway. Some of them are literally 30 seconds apart by foot, who needs a magical teleport? And why do they only exist for the player characters?) This is mostly for immersion so that the world makes more sense and feels more real. But I'd also like to play with non-safe camps with chances for random encounters on higher difficulties. A Fatigue system that would account for distance traveled could easily stop you from always going all the way back to a safe camp. You'd just be fatigued again when you come back to where you were. Put a stop to the silly the back and forth between the camp and the Underdark.