Jonas is a unique player and individual on this planet.
Highly under rated as an player and artist IMHO.
He is defiantly breaking the stereo type with using a 15" for the type of music he is treading on. However I still have of reluctance of using a 15" at all in bass rig. To me they almost always sound "limited" so to speak and the long winded point I'm trying to make is that I think his gear is might be "tailored" for him and his approach. I'm curious what the "Jonas" cabs would sound like with a solid state head and not the pre that was designed to work with it. Or for that matter would that 15" sound any good

? Take a look at where His right hand is positioned and where his 'single' pickup is. Its pretty far back and maybe he needs that 15" just to get some of the "umph" into his transient attack.
I'm looking forward to checking it out at NAMM this year.
Then the speculations can stop.
Also looking forward to a new cab myself that is a spin of the 322 (obviously using 1 12 and 2 10s) to use with the MKII (but yet other gear as well).