The benefits you list are nice, but a video screencast has a couple of big advantages: (1) it sits still until you decide you want to play it. Animated gifs are distracting when you're trying to read the surrounding post, and the more such gifs you have the worse it gets. (2) you can rewind and replay the bits you don't understand.

Are these problems solvable? Could they be solved by this tool?

The first one seems solvable just by having a still shot with a play icon on it that swaps out for the gif when you click it. The second one seems hard.