I think I'm going to do something similar with tmux and i3. Do you have a config you can point me to?

I'm thinking I can have a key combination load a config file, which will include loading the command mode key bindings and some visual indication of entering a command mode; another key combination unloads them and returns to an "insert" mode.

Sure, just put this somewhere in your i3 config file:

  mode "pause" {
      bindsym Escape mode "default"
  }

  bindsym $mod+p mode "pause"

That should show a 'pause' indicator in the i3 bar when you press $mod+p, and unpause when you press escape

I wasn't even thinking of it, but this would be an opportunity for me to go back to dvorak. I switched to qwerty when I started using vim.

I haven't had any problems with vim and i3. i3 behaves sanely. It's adding tmux between them that is muddying the waters.

okay. From what I understand there's significant overlap between i3 and tmux - why do you need both?

detaching and reattaching sessions.

maybe the dtach utility would be helpful.

It's basically just the detach / attach functionality of tmux or screen, without any of the window/frame handling functionality.

(often paired with dvtm but will also work for other setups)

I think I need to sit down with a list of available behaviors and default keybindings and parallelize them, leaning toward keeping vim's default.

But, even better, I think I can make tmux and i3 modal by mapping config switching to a keybinding. In this way they can be put into a command mode and all keybindings in command mode can be shared. Include a visual indicator and I think it'd work really well.