Daniel, While your ideas are great in theory, the details make them impractical. Electrolysis of water (H2O) to make hydrogen (H2) can be done with an electrolyzer (essentially a fuel cell stack), however the speed at which they can produce H2 is determined by the size of the fuel cell stack (the number and size of the catalytic plates). If you look at the amount of energy you need to shed in a short amount of time (Power) to capture regenerative braking, you find that it takes a huge fuel cell stack. These catalytic plates are coated with platinum, therefore, cost minimization requires minimizing the plates.
Perhaps a solution would be to use a battery or ultra-capacitor to capture the regenerative braking energy quickly, then slowly transfer that energy to a smaller electrolyzer. But then one might ask what the benefit of the electrolyzer/fuel cell would be since one could simply use the energy that is stored in the battery /ultra-capacitor.
Note that today\'s fuel cell cars (such as the FCX) use the smallest fuel cells that they can and use a battery (or ultra-capacitor) to capture the regenerative energy and to provide extra power for acceleration, just like a conventional hybrid.
Your solar cell idea also fails when you see how little energy can be collected from the amount of sunlight that hits an automobile.
Keep up the thoughts though!