This is a bit futuristic for Trigger, but maybe it'll inspire someone.
Other rally games (McRae rally, I think) feature car damage. The Trigger car is remarkably enduring, perhaps fabricated out of some alien alloys, and it always finishes without a scratch even after several wipe-out accidents and falls from the mountain top.
We could introduce engine and chassis damage in Trigger, measured in percentages and applied as performance penalties. This may require a lot of fiddling with different values (or even introducing new concepts into the code) that would suit a commercial game with resources and less an opensource one. But who knows.
If we ever implement the above, it would then be nice to have collision detection, especially for trees.