foxyrider wrote:I don't think your spec is worth pusuing at all -
not waterproof? use a dry bag - surely thats adding extra weight?
Solid plastic back? thats not going to be light.
Universal strap? sounds like something from the 1800's
All those straps and pockets sound like a recipe for disaster.
It might be your ideal bag but i don't think its a commercial proposition - i sell cycle luggage and i've never been asked for anything even remotely like your design

Waterproofing a fabric adds more weight than a dry bag. Not in the weight of the coating, but in the implications for fabric weight and weave.
Plastic back - 80g - indispensible, as a pannier going into wheels is not a good idea.
Don't understand your comment about something from the 1800's. It's not dissimilar to the Arkel method.
Pockets - one of the main complaints found on forums about Ortleibs is the lack of pockets.
Straps - not a problem with correct design.
People don't ask for it because in an internet savvy age, they have probably already Googled for luggage and seen what's available. It's also the most quoted reason for stifling innovation. I've built an expedition business based on innovation and listening to users needs. In terms of weight and modern materials, the cycling luggage market is way behind what most other outdoor users want and expect.