I agree with your last point. However, it's hard to change the structure. At one point it was suggested that there be three options for the jury to consider: Guilty; Not guilty or Not Proven.
The problem is, unless it's clearcut the jury would avoid a guilty / not guilty answer.
'Not proven', would also allow a retrial based on the discovery of new evidence.
Anyway, too late for McDonald, but I still think something sinister awaits him with the other charges.