I know it's maybe not an easy one but honestly I can't imagine a 2021 without it now. It started with the ( sorry, no it's not an advertisment for the game ) Seven : https://store.steampowered.com/app/471010/Seven_Enhanced_Edition/
Seven was made by brilliant (fired/quitting ???) CDPR people who are now working from my point of view, on the very good upcoming Baldur's Gate 3 and they probably did bring Verticality mechanics on that one.
So, I was impressed from that brand new real feature such I was for Conan Exile verticality from Funcom.
PS : Sorry for the history and names but it had to be said. I do value and credit the good work.
Could you elaborate more on what you'd like to see for verticality?
I made a photoshopped example from an ingame screenshot to illustrate his idea more obviously:
In my opinion the verticality can include such features:
1. The ability to build multifloor buildings.
2. The ability to build underground basement using shovel (i think the game's engine already has the ability to deform terrain dynamically, because i saw that it creates small pits when you dig the mushrooms for example, so it is technically possible to use the dynamic terrain deformation for underground buildings and perhaps some other landscaping abilities - like flatten terrain (to make some places buildable), dig defensive trenches (to slow down the enemies), etc...
3. New indoor structures: stairs (like on the image), vertical ladders, elevators (requires energy to work).
4. Also add some multifloor Brachylon buildings in their cities perhaps.