What were basicly doing is replacing the plasma rifle with your vehicle of choice. Then setting the plasma rifles spawn time to almost never.
Things you need:
1. HMT
2. 60 plugins pack, or 64
3. Sparkedit
How to do it:
1. Open HMT and open any map, for this tut im using hang em' high.
2. Scroll down to the [vehi] tag, click the +, then click on warthog.
3. Up near the top of HMT look for the meta number (ex. B48928)
4. Copy the meta, Ctrl+C, now go to the [weap] tag, click on the +.
5. Find the plasma rifle, up at the top again, paste the warthogs meta over the plasma rifles meta, click save.
6. Now scroll up again and find the [itmc] tag, click the +, lol
7. find item collections\single weapons\plasma rifle, click that and you should see something saying "Respawn Time: 0 = Default" on the right.
8. Set that number to 9999, click save again.
9. Close HMT, and open spark edit, move the plasma rifle to anywhere you want.
10. Enjoy a new invisible vehicle, which the camo will fade if you shoot it, like the spartan.
What it looks like

Fades

The turret glitch


Note: There are some glitches with this method, sometimes the warthog will not drive, when you shoot the turret it stays shooting, and stays aiming where you left it. Never tried it with a tank, so, yeah... But the ghost should work fine, sometimes you cant get into the vehicle... so, just a warning lol.