It would be a big improvement if Larian (or modders) could just add colorization options like the "dye" options for Geralt's armor sets in The Witcher 3. That was nicely integrated into the game. You didn't immediately get color choices, you had to find the various dye colors in the world or buy from merchants.
I could then make my Rogue's leather armor black instead of brown as a bit of user customization. It might not be as useful for the metal armor sets, but great for leather and wizard robes. And it wouldn't require completely new designs, just a change in the color palette.
A dye system would be so freaking awesome.
The highest priority for me would be clerics and paladins. To be able to have the regalia/symbol of their deity/oath on their armor.
Back to variation,
For classes like sorcerer, monk, and wizard (no armor proficiencies) it'd be fun to find headpieces, accessories, etc. to wear to fit the character aesthetic you're looking for and a good variety of simple robes.
For classes like bard, rogue, druid, and warlock (light armor proficiencies), I really like the uniqueness of what was done for druid. I would like to see something similar for warlock, rogue, and bard.
Yes...So much Yes!