Have you heard of the idea of "Anti-Frustration Features"? Lots of games do little things which are not realistic, but are done because this is a freaking game and games are supposed to be fun. The less tedious busywork you have to do which adds no interest in a game, the better.
If it was not possible to grab so much stuff, there also would not be a need to send stuff to camp. I think the game could even be more fun to play if you had to make choices based on your ability to carry things with you.
I would like at least 5 people in the party as well, but that's not likely to happen. What is your suggestion for "make them sensible in the game world"?
It is not about the actual number, its is about having a reasonable explanation for the limit. For example, in a space sim the planetary landing craft could have a capacity of 4, meaning that only 4 at a time can go adventuring. It is up to Larian to think of something for BG3, but it should not be impossible. Maybe there are only four teleportation crystals available? And everyone agrees that teleportation crystals are indispensible for the exploration party?
14) Short rests are very strange: how can you fully heal by standing still for less than a second?
Game. Time doesn't pass in the game. Do you want to wait around a real-time hour for the rest to complete? I doubt it.
Of course not. It had not realised yet that time does not pass in the game. But then I don´t understand the need to have two different kinds of resting, with one of them having cinematics and the other not.
16) When zoomed out, the camera is able to show a lot of the game world. Much more than the playable characters could see in reality. It would be nice to have a first person view during exploration, and switch to overhead view during combat. And maybe faraway landscapes and objects could be made more hazy? Also the mini map shows info on charcters that are not in the line of sight.
That will still mean needing to add a lot more stuff to the map for those "hazy, faraway landscapes", or expanding the map sizes to accamodate the far-away stuff. Maps can only be of a certain size to avoid causing performance problems. Lag isn't very immersive either.
In general, too much is shown. Reducing visual information should not lead to lag. On the contrary. When you are hidden, the game demonstrates it can determine lines of sight. Perhaps a solution could be to just not display things to which the active character has no line of sight, and increase blur/haze for faraway objects.
17) Given the various personalities of companions, and the urgency of the tadpole problem, it does not make sense for them to hang around the campsite doing nothing while a party of 4 goes exploring. Can they be performing other tasks somehow? Hunting and foraging perhaps? Or be recovering from wounds?
Not a terrible idea to make use of other companions for foraging and such, but what wounds? Even if wounds were a thing - which they aren't, not even in the tabletop - there's no guarantee that they'll have wounds?
Well, people needing time to recover could be an incentive to rotate people in your party. But if there is no flow of time...
I think two immersion problems could be solved in a single stroke: Have the party travel with a cart that is pulled by horses for example. The cart can carry all equipment and it allows a camp to be set up at safe locations. Of course the cart can not enter dungeons, so it will not be possible to loot 20 goblin shields from a dungeon without some serious running back and forth. But I don't think I would miss that. It is entirely reasonable to loot only gold and jewels from a dungeon.
Stil, a more permanent camp would probably be needed for the inactive characters to reside.
You talk about immersion, but where did the party get a horse and cart from? Would they have it on the beach at the start? Do we need to watch the horse and cart move all the time? Will monsters be able to kill the horse?
You would need to earn your bagage train through a quest. Before you find a bag or more serious means of transporting goods you can not carry so much. I think that would actually improve gameplay. Guarding the horse and cart could be a task for those that are not allowed in the party, possible solving that other immersion problem.
There is a limit to how much realism can be put into game, and much of what you're asking for would add tedium for no gameplay benefit.
I am just offering some suggestions from the top of my head. The game developers should be much better at coming up with solutions that increase immersion and do not hamper other aspects of gameplay.