Nicely done, I'd love to see something like this here in the US, but something tells me the UL might have something to say. Definitely doable, just hoops to hop through.
Very similar to a sound crew's bento box(common nickname for a 20-30 amp power distribution panel) or a small generator distribution box. Main difference that I can see is that the bento's and small PDP(power distribution panel) I'm used to are 3 phase input, letting you get, for example, six 20 amp 120v GFCI outlets off one 30 amp 208v input.
I guess one of my big questions is this, is there more to the innards than essentially a power strip and a recoil reel? I ask this because my main problem with power isn't having enough outlets. My main power related problem is too much load for a single breaker. In many of the houses I work at, I wind up having to run extension cords from different circuits or even bringing in my PDP from my generator and plugging it into the dryer or stove 3 phase(I prefer using the PDP if I'm going to be running floor sanders or grinders that use standard current. The big concrete grinder I rent sometimes needs it's own 3 phase connection). I originally bought my PDP and generator for a series of foreclosure cleanups. It's oh so fun ripping down to studs n sheeting with no power or water.
All that said, I think the ultimate systainer PDP for me wouldn't be that hard to design and build. First off, start with a sys 4 or 5 so I've got room for two cord reels. Why two? I want two legs, so I can run it off of two circuits. Next, each leg should have at least two pairs of outlets. I'd be down with a reel-less model as well, if I couldn't get a decent cord length on each reel. If I only get 20 feet on whatever reel that fits in a sys 5, well, why bother, I'm gonna be dragging out the extension cords anyway. Each leg would have one set always on, and the other set of outlets would be paired with a relay so that when leg one energized leg two was kicked on. This would allow for tool activated power on like the vacuums, but with the tools being on separate circuits. I really don't feel the need for a radio, but that's personal preference. I might like the radio better if we actually had any decent stations here. One thing I might add, if there was space left in the box would be an air manifold, possibly with a regulator. I have a Dewalt Quadraport Manifold that I use and like already, but integrating it's functions into the power sys would make for one less item to have to cart around.
If going reel-less, I think I'd stick with a sys 4 or 5 and add in some other odd options. Divide a sys 5 in half down the middle vertically and you could fit the power and air fiddlybits on one side and have sleeves for one or two small extinguishers on the other. Or 3/4 of it is power/air and the other 1/4 of the sys 5 would have an extinguisher.
That raises an interesting question, how many of us actually have a fire extinguisher that we take with us? I think that might deserve it's own topic.