To answer my own question.
I checked it with different dealers and experts, and all of them said that if I want to use it on regular basis, I should consider inflatables as toys. Also here in Switzerland, it counts as a flotation device, and is not allowed more than 150 meters offshore. I bought myself a hardshell kayak for about $300 more, and next Monday I will paddle the first time to work. Let's see how this turns out.
It's been now 3 weeks, my hands are a bit sore, I lost 2kg, and I'm feeling better than ever.
I was lucky with the weather so far, except one little storm, which was pretty exciting and gave me a good adrenaline rush.
I can store the kayak on the shore, because pretty much everyone was so excited to hear that I'm commuting with it, that I even got a place for it with a roof for free. If it happens that you'd be able to commute by kayak, do it! It's the best anti-stress activity ever. It takes me around 5 minutes to get it in/out of the water and crossing the lake is another 15-20 minutes.
The equipment I use right now
- Paddle float for emergencies
- Water pump for staying dry when a wave hits me
- 360° flashlight for visibility
- Headlight for additional visibility when it's dark (sometimes I work until 10pm so it helps me get the kayak ready too)
- Crewsaver life vest
- Werner carbon paddles
- Wheels for easy carrying
- Splash protection (you'll definitely need that if you want your pants to stay dry)
- Lid for storing the kayak and keep it dry inside
- Security/tow-line to prevent the kayak from floating away in case of emergency
- Dry bag
Here's a video of my morning (around 7:00 am): Kayak Lake Zürich (YouTube).
Bought a drysuit for winter, since the water got very cold and if I'd fall into it, I'd have less than 5 minutes to get back in before having no more power left and drown.
After nearly a year of commuting by kayak I paddled from Zürich to Amsterdam, it took me 17 days to get there and I got some valuable experience out of this trip. For electricity I used 2 power banks in combination with a solar panel. Next time I go on a trip like that I'll look into buying new wheels for the boat, as you want the axis in the middle of the boat so you don't have to lift the whole weight of the packed boat.
The Rhine is a wonderful river to travel on, although there's a lot of traffic on it; but if you know how to handle it, it's no problem at all. I'd never paddle the Rhine-Amsterdam Canal again because there are no places to get out, the waves can be lethal and the wind will tire you before you know it (it's the Netherlands which means the wind blows from the ocean inland without being slowed down by forests or mountains).