Amazon 600-Gs are shipping, just got my notification today and I'll have it Monday. Unfortunately, I leave town Monday for a week on a business trip :(
Definitely interested.
Regarding the zipper top though...
With the strap change to be sides of the case, a zipper top wouldn't really be needed. Personally, I like the current flip over top, and instead of a zipper edge, I'd look at a Velcro or even light magnetic closure for the flap.