GAME FEEL
How do we want the game to feel when playing?
All vehicles should feel fast, but depending on the type and size of the vehicle, some will feel slower or faster. For example, the tractor won't actually be slower, but it will give the sensation of greater slowness compared to driving a quad, for instance.
This could be achieved with on-screen visual effects, such as modifying the FOV of each vehicle. In the case of the tractor, since it has larger wheels, this could be indicated by making it lift more dirt than the rest of the vehicles.
Collisions
In collisions, if a player is moving at a very high speed, they should not slow down, as this could be considered a penalty. Instead, the other player will be penalized, since the one ramming is fulfilling their purpose of damaging the enemy vehicle with their speed.
Map
The map can have different areas where ramps with speed boosts, etc., can appear randomly.
The map will include elements that create the illusion of speed changes, such as a muddy section that makes the vehicle "slide" a bit more or slow down.
Audio
Each character would have different catchphrases depending on the action they perform. If voices are not added, a similar approach to Animal Crossing or Mario Kart could be used, where characters have dialogue but not in real languages.
There will be ambient SFX, such as engine sounds, gunfire, construction noises, etc.
When little time is left, tension-building music can be added.
Music for the main menu, victory, defeat, character selection, etc.
Unlockables
A skin or "re-color" could be unlocked when the player achieves certain milestones, such as "Play 5 matches."
In each match, players can collect skin fragments. Each unlockable skin consists of 5 fragments, with 1 fragment appearing per match, ensuring that a full skin cannot be unlocked in a single game.