So, it seems that if you get disconnected from the internet during a game you can continue your offline match vs bots.
After the current bot match ends you get dropped to the main menu and you can even start a new local offline match with no issues.
But if you quit the game and restart it while offline, then you're basically locked out and can't get passed the online profile verification menu.
So everything is implemented already for OFFLINE play vs bots, and works fine. What needs to go is the initial profile check (only) for local play vs. bots.
OFF-Topic: I solved my severe stutter-issue by disabling G-Sync for Sandstorm and choosing fixed refresh rate (120Hz) from my nVidia control panel. Also, enabling V-Sync from the game menu. It seems that currently there are issues with Sandstorm and G-Sync. The difference in game smoothness and frame times is huge.