The “bonus of no gas” is only relevant if you intend to do all of your cooking inside the van - 90% of ours is done outside, hence, whilst I like the idea of the Wallas, it would be no use to us as we'd still have to carry just as much gas.
Another consideration, watching the excellent video posted above, is the amount of space that, together with the fuel and power lines, the air intake and exhaust seem to take up between the cooker and the outside - quite a lot of the cupboard (or whatever) below the cooker looks like it gets taken up with theses, negating much, if not all, of the space freed up by not having gas. Even if you can position them to get them a bit neater than in the video I suspect the heat from the exhaust will restrict what you can do with the space?