This was definitely of interest to me, as it's effectively a LWB version of the Club Joker City I have, the example in the video is even the same colour/wheels/graphics.
They seem to have put the extra space to good use, with quite a bit more storage and a bigger sink, in addition to the L shaped seating. On the downside, that front bed looks a lot less comfortable as you lie on the contoured surface of the seats, rather than the 2 seater RIB style in mine that folds over itself and leaves a flat comfortable mattress on the other side. The trade off is obviously a great seating area though. The shower base also, curiously looks smaller than mine and only has one plughole whereas mine has two, so that it empties easier when not level. I also have the Frohli "sleep system" plastic springs on the upstairs bed and while they do add a bit of comfort, don't get carried away thinking it's going to be like your bed at home cos it isn't. In fact they've used them so they can get away with a thinner mattress (30mm - without which the roof wouldn't shut - seriously, you can't even leave a thin duvet up there) and it is 'just' comfortable enough to sleep on, rather than making the bed luxurious. The amount of storage in mine is fantastic, and the extra in this Kepler is impressive.
To address a couple of points above, yes it does have a fridge, it's the same Dometic model I have. It's small but big enough that I've never needed more space.
Also, the shower - yes it can be a bit tight and hooking the bulky shower curtain up is tricky, but it does work and having the facility is useful - it doesn't take up any space if you're not using it. The biggest problem is how you dry the curtain afterwards, after all if your're showering inside it's probably cos the weather is crap so you can't put it outside to dry. If the weather is good, the showerhead just suckers to the inside of the tailgate so that you can open it and shower outside. It's a much preferable option and what I try and do most of the time as the curtain isn't needed then. The hot water (electric only) is just 300W only, but gives just enough water for one shower and doesn't deplete the battery as much as you'd think, though I try and switch it on 20 mins before getting to my destination if possible so that it's being topped up.
I agree the Westfalias aren't for everyone, and there is a lot going on in a small space, but it is another option, and having more choice is never a bad thing. What attracted me to this over the California (which I considered at length) was that I knew what I wanted from a van. It was never going to be used as a day van or general transport, but would be used to camp all over Britain and Europe/Scandinavia where there were no facilities and for me this was head and shoulders the best option for that. Having said that, although there is just as much floor area as in any other camper conversion, it is arranged differently meaning juggling where you stand sometimes. As I only have either just me, or sometimes my 3yr old grandaughter with me, then I can get away with it but if you were travelling as a family/couple I can see where the extra space of the Kepler would be very useful.
This wasn't available when I was looking but for important reasons, it needed to fit in the 5m/2m package size so couldn't consider a LWB.
Makes me wonder about the price though, the shower and downstairs bed were additional options (as were loads of other things) on the Club Joker and I couldn't run to the £2.5k they wanted for those leather seats when I bought mine pre-euro crisis as the price was already scary. As everything seems to be standard on the bigger Kepler One and the the £ is in the skip, I'm guessing this could top £70k?
EDIT: Looks like I'm wrong on the price, there's an unregistered one with the same engine/DSG as mine going for £66.4 so pricey but not insane. Also the residual on Westfalias is very good, I've recently made tentative enquiries as mine may have to go in October and now receive regular calls from two dealers asking me to please give them first option to buy at damn close to what I paid for it!
If they are for UK market why do they have the death door on the offside opening into the road? I don't understand this as well as on the California. All uk spec motorhome vehicles / caravans open on to the near side pavement for safety. LWB will limit appeal, but looking at the website it is competitive on price, but the 6 looks more versatile.