Steve,
I know you mentioned that you don't want the sides to be blacked out but consider this...
Inspiration from Finescale back in the late 80's, I build a box diorama. I had a 1/48 scale P-40 making a fly-by of it's latest victim, a 1/72 Bf-109 sitting on the ground with smoke coming from the engine.
Here's a quick proposal of the idea...the picture here will be from the front view only. Sides cannot be seen, of course. The ground will gradually rise up to the back of the box and painted an ever-lighter color, simulating the hazy atmosphere.
Like I said, I know you want it to be seen from all sides, but perspective will not allow it to be pulled off effectively.
EDIT: Oh yeah, make the smoke by bent wire and gluing cotton (or lint from your dryer) to it and spray-painting it black and dark gray...it looks convincingly real.