One word: Overpowered.
This seems like the first 2 people mod making game to me. That's good enough for me to support a mod
If you want lots of ideas, go to the Doom/Aleryon mod thread and search through what I typed.
And for some random stuff...
Motor oil, barrier, oil barrel, flames,...
Also having parts, weapons, and enhancements attachable to your vehicle.
Let's say your vehicle has 100 PP (Parts Points; need to find a better name). Armor augmentation for +3 HP costs 1 PP. Putting in dual machinegun would cost 40PP. You can not put more weapons than the max amount the vehicle can take. So lets say this limit is 3. You used up one of them and can only put 2 more. Engines, wheels, and such would also have a limit.
Now for the enhancements. These do not cost PP and permanently stays attached to your vehicle. This can either increase amount of PP, weapons max, more HP, whatever. You can, however, find more vehicles along your way and switch to other vehicles if needed. Such as you have a crappy passenger car and want to switch for a mighty tank. Enhancements are permanent so you need to choose the vehicle you're going to use for your killjoy ride, whatever that is.
For the vehicles you might as well as use...
Helicopter, hover vehicle thingie, plane, jet, and missile (?).