You can use this plugin to get the same mappings in insert mode for Vim:
Oh, if you like those bindings in insert mode, you are probably already aware of Tim Pope's vim-rsi [1] plugin. If not, check it out, it might have some interesting bindings you aren't using yet.
> it genuinely interests me how Vi users put up with the constant need to strain their pinky to switch to command mode.
Is it any different from how emacs users put up with Ctrl/Alt?
You aren't looking to switch, but if anybody is, install this https://github.com/tpope/vim-rsi for basic keybinding in insert mode. This is quite a short file. If you want, you can simply copy it to your .vimrc. For non-basic movement/editing, switch to normal mode and edit.