Oooh, really now? Damn, the modding scene is hitting this game like a bloody Mack truck, Creation Kit or not. Well... for one, something in the same vein of SkyUI/DarnUI for Skyrim and Fallout NV respectively. While I like simplicity... I never really liked it in my Bethesda titles, and rather enjoy the complex list of menus, sorting function, and more complete keybinds (as vanilla Fallout 4 does seem to have some points where key presses won't register).
...Then I'd like to see HUD addons. Weapons with ammo counters even... attachment perhaps.