I think the ideal situation would be one in which January exams are still available, and one is permitted to resit an exam as many times as they wish - but that whenever they declare their grades to a university or employer etc. they have to mention the number of attempts they had, and the results of their previous attempts if they're asked (or perhaps this information should be available on the certificate).
This would mean that candidates who got good grades first time are distinguishable from those who took several attempts (and the university or employer can place whatever emphasis they deem appropriate upon the number of attempts). The more information the university/employer has, the easier it will be to decide whether you really are a suitable candidate for their offer. Also, it makes it fairer for the people who were able to succeed in one go, and it discourages people from sitting exams when they're not ready for them.
But it also means that candidates aren't stuck with the first grade they get. Normally in a scientific experiment, if you want to test something, you repeat the experiment over and over again to get reliable results. If you want to test the height of Chinese people for example, you don't just measure the first one you see, you do it over and over again with lots of different people. Similarly, a test of someone's academic ability should allow for them to resit an exam, so they're not just assumed to be academically incapable just because of one unfortunate, anomalous result.