Cheating is a concern, but it is important to understand that the handicap system is not designed to, nor can it ever, stop cheating. The only people who can stop the cheats are their fellow club members and their golf clubs which must take disciplinary action.
The South African handicapping system is based on the USGA one and is aimed at the majority of golfers who are honest. It would be excessive to change the entire system to try and eliminate cheating by a small minority of golfers.
A key way to combat cheating is for clubs to open all rounds on the system when players check-in. This ensures that the players have to enter scores, or face a penalty.
The scores of all players with a handicap are available for everyone to see on the system. This peer review is a critical element in reducing handicap manipulation, as anyone can check on a suspected cheat to see what score was entered.