Seems maybe author did not know that this is already built into vim?:
"easy vim", aka evim, or "vim -y". see "man vim"
That said, if modeless editor you are looking for... then vim is not the editor you're looking for. It goes against what vim is, and hamstrings it. Learning vim is a journey, and once comfort sets in, you will understand why, why vim.
The real magic is opening :term, close all your splits, forget that you're still in term, try to open vim again, and then being momentarily confused why you find that all the keybinds and broken. This happens to me about once a month.
Not the first, not the last hacky project. Saying that it goes against what it is makes me think of JS V8 being used outside of browser.
Perhaps there are good reasons for not having modeless vim (or server side js for that matter), but the industry overwhelmingly accepts good enough solutions, with good enough results.
"easy vim", aka evim, or "vim -y". see "man vim"
That said, if modeless editor you are looking for... then vim is not the editor you're looking for. It goes against what vim is, and hamstrings it. Learning vim is a journey, and once comfort sets in, you will understand why, why vim.