I've had similar concerns and I agree with a lot of this.

Get this closer to a 7th grade reading level. This sets a low bar at potential readers who can understand 'blockbuster' books in English. (This might be accomplished purely with the terminology concern/change above)

If we really want to approach a 7th grade reading level, then we had better aim for kindergartners. I remember reading through the book trying to imagine how to bring it down several levels and thinking about just how many words I was taking for granted as a high-IQ adult who has had plenty of time to just passively soak up vocabulary and overviews of highly complex fields. I just don't think we're there yet; I think that's why there are things like SPARC where we're trying it out on highly intelligent high school students who are unusually well-educated for their age.

Change all hyperlinks to footnotes.

To my knowledge this is already a priority.

Is there any ongoing attempt or desire to do a group edit of this into an 'Accessible Rationality'?

I find that there's a wide disparity between LW users in intelligence and education, and I don't know if I see a wiki-like approach converging on anything particularly useful. I would imagine arguments about what's not simple enough and what's not complex enough, and about people using examples from their pet fields that others don't understand. It might work if you threw enough bodies at it, like Wikipedia, but we don't have that many bodies. I don't know how others feel.