The easiest species to obtain in SA is still the Veiled. If they are kept carefully, with attention to diet, temperature and lighting, then they should not suffer from MBD. That is if you can get good stock to start with. Panthers are a superb chameleon with less MBD risk. The risk, to a great extent, is related to the speed of growth - people often overfeed young Veiled which then grow faster than the calcium can be absorbed. Panthers typically grow slower, hence the lower risk.
The risk is often compounded when they are very small, i.e. below 4 months. At that stage it is easy to get a lot of growth and it is also easy to provide incorrect UV and insufficient spupplements. The answer is to check who has had them before you buy them. Who bred them and does the pet shop have the right set up while they wait for them to sell. I have seen some very good pet shops in SA that I would have no problems buying from; they know what they are doing and care properly for their animals. It is up to you to check!
Carpets were always our favourite as they were smaller and had great 'personalities' - and bred like rabbits! But I believe that they are not easily obtained in SA any more.
Whatever species you get, if you provide the correct care, you will have an awesome pet.