Why not allow people with HIV, Hep-C, etc. to donate blood. However, that blood could only be transfused into people who were ALREADY INFECTED with HIV, Hep-C, etc. It would have the additional advantage of increasing the supply of uncontaminated blood for uncontaminated people. We already classify blood for type [A, B, AB, O] and Rh, so this would just be another sub-classification.
You want to put infected blood into the system? Screw ups happen. Even if you clearly marked the packaging, I see a tragedy waiting to happen. Add in government run health care and it would be like playing russian roulette with a 1911.