[Izkata]

> And we are only talking about editing model (e.g. b being beginning of a word)

nmap can shadow the built-in commands, replacing them with whatever function you want.

> There some cases were Neovim already wants to disconnect itself from vim legacy like allowing to scroll viewport without moving the cursor

I think you mean beyond where the cursor is so it's hidden, but you can jump the screen so the cursor's current position is at the top/middle/bottom without moving the cursor using zt/zz/zb.