i don’t have much knowledge about flamingo but vray for rhino does support ies light files but not volumetric lights. in this case you described volumetric light is what you need so you need to find another solution (Photoshop etc.) to achieve desired effect.
Interesting question. Can you post a sample image of the type of lighting you’re after. Also do you have an IES file that you’d use? I think what you’ve described would be possible in a variety of render plugins…