Regarding armor class:
Many players (rightfully, in my opinion) complain that BG3 differs in many cases from the DnD 5E rules. Looking at shove as bonus action, proper reactions and so on.
I am happy that they did not mess with the armor system as well.
I see no reason to make the armor system more complicated and I fail to see the advantage the proposed changes would bring.
If you want to manage several different armor types, remember how they stack or not, and which of them are applied when flat footed or touch attacks come into play: Play Kingmaker or WotR.
I do not say DnD 5E is perfect.
They made many many things more simple compared to DnD 3E and I can understand that some players complain about it.
But looking at many comments from players, 5E is already difficult enough for them, especially since BG3 is really bad in explaining its own rules.
Prof. Dr. Dr. Mad S. Tist
World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already
