One of the things that's always bugged me about D&D and d20 games is the laundry list of weapons and armor. Some people really like them, I get that, but the way the lists are designed, there's clearly a "right" choice for each. The longsword with it's top dog damage and proficiency bonus in 4E, and plate + shield with it's top AC bonus and minor drawbacks.
I agree with this somewhat. There's no point in offering dozens of 'choices' if one of them is clearly the right answer.
In theory, I liked the 3e model for weapons, where the longsword and battleaxe were similar but not identical - they did the same damage but had different critical modifiers. Thus, there was a trade-off - did you want to crit hard, or often? (Of course, it wasn't perfect...)
Conversely, I
didn't like the 3e model for armours, where there were several different Light, Medium and Heavy armours, but in each case there was a clear 'best' choice. I don't think I ever saw a character who wasn't wearing leather, masterwork studded leather, or a mithral shirt (Light); the breastplate or mithral full plate (Medium); or full plate (Heavy). The other armours might as well not have existed.
I thought 4e had the armours about right - each category of armour had an associated feat, and each category was strictly better than the one before. However, all armours within that category were equivalent, in terms of cost, AC bonus, skill penalties, and so on.
What if in the basic core of 5E you have weapons and armor as a style choice instead of a laundry list of bad choices with one clear best choice? What about making damage and AC a class feature. Fighters get mid range damage and top tier AC, but the specific weapons and armor used is completely up to the player.
Mathematically, that would work, although it leads to "no armour" being the optimal choice (no cost, no encumbrance, no skill penalties, and you get the full benefits anyway).
However, I very much wouldn't like it.