The latest version of the demo allows custom offline multiplayer matches. The only available map is the lobby, but all of the game variant options are present. With a little tweaking you should be able to get a decent bot match going.
It also includes a few changes that will be in the next update in the main game:
- AI now works in lobby
- Mob emitter placed in lobby
- More weapons placed on lobby
- Post-match timer is now 0 seconds by default instead of 15, so you'll go straight back to the lobby instead of hanging around with broken animations
- Sticky grenade material is (slightly) less ugly