I have heard using 2-3 khorne troop choices makes for a prety good adition to a shooting army.
I dunno about troop choices, but the feel no pain demon prince/bloodthrister combo backed up by shooting is a pretty nasty combo. A unit of khorne bikers matched up with a shooty force is pretty brutal too, with or without bloodletters. But as far as Bezerkers, don't think a unit or three of bezerkers would be worth it. Really need a horde of them to be of much use, what with them wanting to do their own thing all the time.
Slaanesh matches up well with shooty undivided, as it can add both solid assault and shooting ability. The one that you see theorized is the 6 havoc squad list (3 elite
MoS havocs and 3
MoCU havocs). Never seen it or used it personally but certainly a very brutal 'hybrid' list.
The other two gods aren't as popular, atleast from a theoryhammer,
WAAC point of view. However either have some advantages that one could take advantage of (examples: manreaper is probably the best daemon weapon, nurgle and rubic terminators are very resilient, about it for
WAAC list)