What made you think Hassan's video will not benefit Arabs?
I'm sorry, I think I didn't read your post carefully enough. YouTube supports subtitles, but the problem is, Flash doesn't render Arabic script correctly. So in that respect it wouldn't be readable and therefore not useful for Arabic speakers. However, it's possible to merge subtitles with the video and there's software that can do that and they support the complex scripts (e.g. Arabic, Hebrew etc.)
Leaving all these issues aside, the problem remains that creating subtitles, checking them for correctness and doing translations takes an awful lot of time. It's not as easy as it seems.
I don't know... Maybe Hassan could dub some of his videos in Arabic. Should be easier.