Rucksack/ panier rack A2 design idea

[M.G]

For an A2 design project im looking at designing, a low cost system for easy transport of a rucksack on a bike.
Aimed at commuters, shoppers, leisure, school cyclists etc; who may have to carry heavy loads of books etc with a rucksack on a bike and on their back. The system would allow any rucksack to be easily and safely attached to the back of a bike, i know there are specific products which cross between a panier and a rucksack but are often expensive and hard to find.
Any one got any comments on the design idea or knowledge of similar products on the market?