I would suggest that thief gameplay should get improved a lot.
Hide in shadows, sneak behind A.I., laying better traps would need improvement to get more dynamic and interesting thief gameplay.
I'm much more a fan of BG1 than BG2 (or more specifically BG1 with SCS and other mods installed), but one thing I did really find fun was using the traps skill with thieves in BG2. I realize you can do it in BG tutu and BGEE, but unless you have like 3 thieves or something you have to spend skill points early on in more basic stufff like Pick Locks, Find Traps, Hide in Shadows, and Move Silently (although I've often wondered if I'm wasting points by puttting them into both HiS and MS when they both do the same thing).
Anyway, I need to look at how 5e handles thieiving skills. But it's heartening to read that 5e hearkens back to 2e AD&D in many ways.
Edit: Just took a gander at the 5e SRD, didn't see setting traps on the list of skills for Rogues/Thieves. Oh well! Maybe they can incorporate it nevertheless.