Let's face it - the PC user interface for the past games (Fallout 3 and Skyrim) left things to wish for.
The font size was a bit too large, the lists of the inventory consequently a little too small, the inventory list - especially after some time playing - a complete mess to navigate.
Modders did amazing things for the UI - up to adding sorting functions to look for specific items (Skyrim) or simple prefixes to highlight item categories (New Vegas). Personally I'd prefer tabs for item categories - including while trading!
As I've just come across it in another thread - save functionality could also be improved. Naming your save games should be a given on the PC, even if it is optional. Bioware does this neat thing where they order savefiles by characters played and let you quick and easily switch between profiles.
Since - let's be honest - Bethesdas games have the tendency to crash, especially once you go mad on mods a robust save feature is much welcome.
I'm thinking quicksave and alternating automated saves at world-space changes and before important events.
TL,DR List
- font size can be changed
- inventory
1) search functionality OR
2) prefixes to better find item of a specific category OR
3) tabs for categories (while trading) - save games
1) can be named
2) quick save
3) alternating autosaves
4) save profiles for different characters - list-form for dialogue (with quick choice shortcuts - 1,2,3...)
- full support for keybinds, including all keys/actions (no hard-mapped keys)
- custom map markers
That's a quick bucket list, I'll add more as necessary.