That's actually an innovative design, but not very practical. This will slow your typing speed to about half, and also require you to rebuild muscle memory. The main flaw is the space bar.
When you hold it down, it'll switch to the other keyboard side, but when you tap, it'll register as a space. When you start to type fast, quick switching keyboard sides with the space bar will eventually start looking like a tap, and it'll turn into a space instead of the switched side function. So now you're capped a certain speed, depending on the threashold of how long you have to hold down the space bar to activate the other side. In addition, If you have a maximum typing speed and now the left hand has to type double the amount of words, then your typing speed will be cut in half. Lastly, just think how much your thumb has to now work. Statistically, every other key now requires you to press down the space bar, in addition to the space after every letter.