What’s the use case? Is there a reason that the disk is not unlocked at boot/login?

I use a gaming-mode for that. Like this:

# Create a gaming mode
mode "gaming" {
    # switch to workspace
    bindsym $mod+1 workspace number $ws1 ; mode "default"
    bindsym $mod+2 workspace number $ws2 ; mode "default"
    bindsym $mod+3 workspace number $ws3 ; mode "default"
    bindsym $mod+4 workspace number $ws4 ; mode "default"
    bindsym $mod+5 workspace number $ws5 ; mode "default"
    bindsym $mod+6 workspace number $ws6 ; mode "default"
    bindsym $mod+7 workspace number $ws7 ; mode "default"
    bindsym $mod+8 workspace number $ws8 ; mode "default"
    bindsym $mod+9 workspace number $ws9 ; mode "default"

    # move focused container to workspace
    bindsym $mod+Shift+1 move container to workspace number $ws1
    bindsym $mod+Shift+2 move container to workspace number $ws2
    bindsym $mod+Shift+3 move container to workspace number $ws3
    bindsym $mod+Shift+4 move container to workspace number $ws4
    bindsym $mod+Shift+5 move container to workspace number $ws5
    bindsym $mod+Shift+6 move container to workspace number $ws6
    bindsym $mod+Shift+7 move container to workspace number $ws7
    bindsym $mod+Shift+8 move container to workspace number $ws8
    bindsym $mod+Shift+9 move container to workspace number $ws9
    bindsym $mod+Shift+0 move container to workspace number $ws10
}

# Enter the gaming mode when a game is started
for_window [class="^steam_app_"] move to workspace $ws10; workspace $ws10; mode "gaming"
for_window [class="^hl2_linux"] move to workspace $ws10; workspace $ws10; mode "gaming"

This automatically moves (most) games to workspaces 10 and switches to that workspace. This allows me to use key combinations that would otherwise be used by i3.