How can I make vim "command mode" the default mode for terminal
No there in no way to start your terminal in command mode.

The set keymap setting is used to customize the keymap within terminal. A line with set keymap vi-command means that mappings below that line apply to command mode; a line with set keymap vi-insert means that mappings below that line apply to insert mode. For more details see: http://vim.wikia.com/wiki/Use_vi_shortcuts_in_terminal

But starting from bash version 4.3 you can change your prompt to highlight which mode you are currently in by putting set show-mode-in-prompt on in your ~/.inputrc file. This with put either (ins) or (cmd) at the start of your prompt. You can further customize it by using command:

set vi-cmd-mode-string "\1\e[1;31m\2(cmd)\1\e[0m\2" -- will give light red color

set vi-ins-mode-string "\1\e[1;35m\2(ins)\1\e[0m\2" -- will give light purple color

You can pick any of the following color by their ANSI codes:

Black            \e[0;30m
Blue             \e[0;34m
Green            \e[0;32m
Cyan             \e[0;36m
Red              \e[0;31m
Purple           \e[0;35m
Brown            \e[0;33m
Gray             \e[0;37m
Dark Gray        \e[1;30m
Light Blue       \e[1;34m
Light Green      \e[1;32m
Light Cyan       \e[1;36m
Light Red        \e[1;31m
Light Purple     \e[1;35m
Yellow           \e[1;33m
White            \e[1;37m