As I said, Elinchrom ELB battery pack & head is weather-proof and extremely compact. I'm sure its not too difficult for them to incorporate the capacitor & battery into the flash head itself. However its true Elinchrom does not have all the Bron's tech.
I just looked on Elinchrom's website and could see no mention of the ELB's water resistance and only a mention of the Ranger RX's moisture resistant outlet caps but don't really know much about Elinchrom's range.
Bron has weather-proof knowhow, as you can see from their HMI, DW200 and DW400 .. completely waterproof both head and ballast. And I think the voltage inside the HMI ballast are crazily high as well.
IP54 so splash proof and can resist some water ingress but hardly water proof and I still wouldn't want to fire a fully charged capacitor around people while in the rain if it's only IP54 rated.