5 is an interesting, simple, doable idea just by modifying keybinds. There are already few commonly done, such as keybinds for laptop, numpad for navigation with 5/0 for z-level tarversal, or smaller ones like Delete key over 'r'emove for manager orders.
As it is a simple text file, it's well within the capabilities of steam workshop. Good idea.
As for the rest, unless Toady One makes UI moddable, they are impossible without (and possible with) dfhack. Also, I can't imagine Toady One will include possibility for things like 2 (simplify) without including them themselves.
In regards to point 1 (Information), there is minor capability for this with reaction descriptions, but that's only for non-hardcoded reactions. Items with
MATERIAL_REACTION_PRODUCT, such as clay boulders and iron bars, also list reactions that use these, but that's somewhat rare. Dfhack also adds some small descriptions.
In summary, I'd say this is "more (moddable) descriptions".
(Also, the example being incomplete makes it somewhat amusing self-demonstrating example.)
In regards to point 3 (stairs), I would want the option to still have just one. There are use cases for having just downstairs (walkable drainage) or upstairs (growing grass only). Either automatically added designation or automatically dug would be doable, with the first one being slightly easier (I guess).
In regards to point 4 (trade), this change would be less of an UI change and more of a game mod. Currently, trade runs on unequal barter based on the internal value of goods and the haggling skills, requests and willingness of participants.
Overall, I think it would be prudent to make a post in suggestions forum if you want to include these in base game, though check whether something has been suggested first - I know more consistency in interface isn't uncommon.