I'm a little concerned about the generous spacing between staves in general. I love it as someone studying the scores, but from a performance perspective, I feel like the more that can be done to keep preludes to one opening and fugues to one or two openings would be greatly appreciated by pianists. There are cases in the old BGS edition where the desire to keep page turns out leads to absurdly cramped spacing. That practice should of course be avoided here. But I think that 5 staves per page could be a norm instead of four, with four and six used as needed.
Paper is cheap, but page turners are not, so "this page intentionally left blank" pages could be used generously (or sell the space as in the open goldberg edition. Or fill it with out-of-copyright poetry and stories :-) or musical analysis. :-)