Speed..!
This is exactly what I meant - an effect derived from the delivery of ordnance but not an individual round strike. The performance saver would be that this could appear after weapons delivery, not at time of impact causing stutter. It could be rendered as per the existing, fast conventional clouds, though with some differences to shape/density etc. Cloud height / colour & shape could vary according to munition, target or land class (if DCS retains land class concept after Nevada).
I think that having achieved such stellar immersion within the cockpit, it would be great if Ed would incorporate some more environmental tweaks to up the realism even further. :)