Not to be a Debbie downer here but I think this is one of the worst ideas I've ever heard.
VLOS means someone has to have eyes on the Phantom at all times while in flight. Anything else is just tossing the dice and reckless in my opinion.
BUT...
This is actually like filming fireworks in a way. You need to get up in the air and shoot a test shot while someone lights the rocket. It may take a couple of rockets to find the perfect spot, but you will.
If you must do this without any trial runs or ground staff than I suggest you find a landmark, be it a tree, hill, river, creek, water tower or windmill that can be easily seen from aloft. Then position the Phantom over that at pre-determined altitude. I believe you can make a mission in Litchi or GO! or AutoPilot to achieve this, although again, I don't recommend it.