I carry a moderate amount of camera gear. A D200, 2-4 lenses, and a flash.
A few comments:
I'm generally uncomfortable with the concept of dividers in a bag that don't protect the gear from other items in the bag. This insert is designed to rest on the bottom of a bag, which means the top of a bag is where books, clothing, and other items are stored - all things that rattle around on top of the $$$ gear.
Speaking of which, you'll have to dig through stuff on top to get to camera gear, which offsets the open design of the insert which is meant to make it easy to use.
The pockets are "tall", but not really tall. That means you can put large lenses in, but probably not stack two moderate sized lenses in the same pocket. No one with a 80-200 F2.8 (or longer) is going to use the insert (too small and there's not enough space for the other lenses you take), so I'd make it a bit less tall to fit the mid-range of lenses better. Maybe its hard to gauge from the picture.
It would be nice to use the dynema fabric somehow. Why? It's resistant to knives and tearing...and anyone who travels knows about those bag slashers...
Put some d-rings on the ends of the bag to attach shoulder straps to - it would allow people to use the bag as a small, open shoulder bag for other uses when traveling.
Maybe figure out how to close the top if the insert was to be used on its own (a zipper?) and some side pockets for cards or filters.
Make sure the base is firm so it doesn't sag and also include padding to allow the bag to be put down a bit heavier than normal and protect the gear (remember, camera gear is heavy and gets thrown down all the time to swap lenses, get the shot, etc).
Be sure to offer a dark, unnoticeable color, along with the catchy stuff. When in an iffy location, i dont want to open a black bag only to catch everyone's eyes with a crimson insert full of thousands of dollars of gear.
Finally, it might be nice to make a half width version so that you can put a camera on onside of a bag, along with a single lens, but then put a large bottle of water/book/etc. next to it, without having to put it into the insert. In other words, share the bottom of the bag with other items.