Usually, I just use the teleporter shrub to summon the ghost, and pause before it can disappear. I then use testing cheats to make the ghost selectable, the lot debugger to spawn the tombstone, and then make the ghost unselectable again before unpausing. I have noticed no ill effects from this method, and the old tombstone does disappear, but i can't say that it's not causing unseen problems.
That's a pretty good idea, i had no idea you could do that.