They don't even have to use all of him.
Just have flaming tire tracks criss crossing all their movies and never explain it.
In the comics, the new Ghost Rider, even though the old Ghost Rider is hanging out in Red Hulk's Thunderbolts, but the new Ghost Rider drives a ghost car with four flaming wheels.
Makes you wonder what other vehicles a ghost rider can ride?
A Ghost Helicopter with flaming rotor blades would be fantastic but imagine how ridiculous a Ghostjetski or a Ghostsnowmobile would be?