I observe this photo, the shuttle is pretty evenly lit.
I propose an approximation to create the lighting effect from exhaust.
Another motivation is that current Engine Lighting mode is to add point light source per engine.
When the number of engines is high, the frame rate is low.
My proposed idea:
1 Add only one light source for all engines, instead of one point light source per engine
This can prevent lag by adding too many light sources when there are many engines
2 This added light source should have a virtual position which can be attached below the center of thrust.
And this added light source has both ambient light source and point light source properties.
Entire scene, which includes ground and the rocket, is lit by the light source with decline according to distance square, like point light source.
However, the lit pixels disregard the cosine effect between incident direction and surface normal direction, like an ambient light source.