1) Open up HMTv3.5
2) Go to the damage tags
3A) Select vehicle hit environment, and vehicle kill unit. Change damage to something that will kill you, and some force so you go somewhere, and don't just die.
3B) You can also copy and paste the scorpion shell explosion damage over the vehicle hit environment and vehicle kill unit. Just make sure you lower the radius and raise the damage so it kills you for sure, and you don't get 500X the force because the radius is so big.
There you are. It kills you and the warthog goes somewhere. If you want your warthog to actually explode, you can change effects, or you can do the following.
1) In the scorpion shell projectile tag, make the weight heavy so it just hits the ground.
2) Copy the shell projectile over the frag grenade equiptment.
Make sure your always equipped with grenades when you run into something.

Problem1) When you die, and you have nades, your character blows up... no matter what.
Problem2) When frag grenades spawn, they blow up. But since you didn't edit the projectile for your frag grenade, you can still throw ones that are in your inventory to start with.
Problem3) You happen to be taking a stroll on top of the bloodgulch base, when suddenly TANK SHELLS START SPAWNING FROM NO WHERE... and you die.

If you don't make the weight of the shell very large, when your frag grenade spawns, it could shoot out to a side.

oh and, please leave comments, I don't post much here, but I am pretty good.
EDIT* If you would like a simpler way, just swap the meta of the tank explosion over the cyborg shield depletion, and make vehicles have damage when you run them into things like before. But people will explode whenever they die, or even quit, thats the only downfall. I don't think their is a fool proof way... although I do know one, but I'll have to test it a lot to get it to work.