[short post :3]
1) having a 3rd copy of ctrl/shift/alt in the middle of the keyboard instead of the corner. the number of shortcuts doable with a single hand could quadruple :3
2) Smite (mythology MOBA) had a cool system with dozens of voice lines triggerable with 2-4 letter combos https://smite.fandom.com/wiki/Voice_Commands . I remember switching to Overwatch with 8 voice lines & feeling limited. you don't have to learn all the lines in smite, since it lists possible shortcuts /while/ you type, a bit like auto-complete in code editors :3 I think it's better than radial menus because your mouse can only be in one place, while you can have fingers on like 3-4 keys ready to press a whole sequence at once.
[bonus], some of my fav shortcuts:
-a good replacement for the "close window" [x] button is ctrl+w (it's fairly standard even) :3
-for accessing lots of important menus, in the same place at once, you can rightclick the start button n_n
-windows+E to open explorer is nice too