I read another alternative AA big book a while ago that attempted a similar thing. It was well written in the sense that it was a much better job than I could do, but it took all of the guts out of the program and presented a sort of wishy washy politically correct version. It also severely edited stories like Bill and Bobs into something they never would have said, and did not experience.
And that is the problem in changing the old book. It is an attempt to rewrite history. All the big book is is a record of what the founders did to recover, the mistakes they made, and the things they found that worked. When it was released no one knew if the book would do any good, but it did. It exceeded every ones expectations. It turned out that the book had something that would interest alcoholics, depth and weight. And that grew as the ideas contained in it brought about success all over the world like never before. It has track record and street cred.
Any rewrite lacks those credentials. It may work but only time will tell. The trouble is when something doesn't work, alcoholics tend to get drunk and some even die. Personally I am in favor of trying everything you can think of, leaving AA till last. You may well find something that works along the way. But if not, the old AA seems to works where nothing else's does, and it works better, if there are no other options left. Then the God bit doesn't seem to be so much of a barrier.