If you prove that HLAI is safer than narrow AI jumping in paper clip maximiser, it is good EA case. If you prove that risks of synthetic biology is extremely high if we will not create HLAI in time, it would also support your point of view.

The idea that friendly superintelligence would be massively useful is implicit (and often explicit) in nearly every argument in favor of AI safety efforts, certainly including EY and Bostrom. But you seem to be making the much stronger claim that we should therefore altruistically expend effort to accelerate its development. I am not convinced. Your argument rests on the proposition that current research on AI is so specific that its contribution toward human-level AI is very small, so small that the modest efforts of EAs (compared to all the massive corporations working on narrow AI) will speed things up significantly. In support of that, you mainly discuss vision--and I will agree with you that vision is not necessary for general AI, though some form of sensory input might be. However, another major focus of corporate AI research is natural language processing, which is much more closely tied to general intelligence. It is not clear whether we could call any system generally intelligent without it. If you accept that mainstream AI research is making some progress toward human-level AI, even though it's not the main intention, then it quickly becomes clear that EA efforts would have greater marginal benefit in working on AI safety, something that mainstream research largely rejects outright.