The B4 Air was/is an AMAZING unit and silly it went away (except when renting where they still enjoy quite a lot of use). The B1x and d2 are great, but do not come close to the endless options which a new B4 could open up. The new version could be;
a) smaller/lighter 1200w/s Pac
b) longer battery life
c) all the current bells and whistles like bluetooth, usb...
d) total weather sealing
I will always prefer using the Pro heads when they are an option (again, always want a round dome instead of flat... seems to be a theme here) and the B4 allowed the perfect blend of studio/location functionality. It also saves 1 sandbag for the stand when you mount the pack, more-better less gear. I literally would buy 2 pacs right now if they were available.