Steelport Racing Club v2.2 released. Added "Fake Co-op Partner" (DX edition only). You can now race against an AI! (push Z key during Race Selector to toggle)... or so it seems.
I'm sorry, but he is dumb and this is the best I could; the game's vehicle pathfind system depends on predefined "navpoints" and "paths" which we cannot add anything new.
The game also supports "chase" mode where an AI vehicle tries to chase a specified human. This mode is what I use, but its effectiveness is rather limited.
(I actually added him to ensure most of HUD stuff works correctly with multiple players.)