Upload & Sell: Off
I'm not the visitor that "wildimages" is, my trips have been multiple times to South Africa, Kenya, Tanzania, and Botswana. Never found a need for the type of redundancy you are talking about. Nor do I know of any outfitters or guides for photo safaris that operate with it.
However.........you will get much more specific and useful info if you provide the group with some more detailed information.........Where are you going, for how long? What is your anticipated itenerary and how will you get from place to place. Which wildlife do you want to focus on? How many people will be with you in your vehicles (this is a BIG consideration affecting your equipment load)? These need to be defined at least 6 months in advance, especially if you don't already have an outfitter lined up. The guy I use works only with small groups (9 or less) in South and East Africa, does very limited travel (no more than 2 locations in 10 days) and is already booking reservations for 2018.
FYI, my current load out for Mala Mala/Sabi Sand reserves and Mashatu or Phinda in South Africa and for Tanzania/Kenya on the Masai Mara is shown below. I have never needed more power (except occassionally for birds in flight or at long distance), as the game guides and rangers will position you for photography, as close or distant as you need to be, constrained only by geography and plant growth (well, at least on those private reserves where you can work off road - very rare these days).
D810 with 80-400 zoom
D810 with 24-85 zoom
D500 with 70-200 zoom and 1.4 teleconverter (spare, and have never used it to date)
a pair of SB910 flashes (you will be out past sunset most days)
tripod - especially useful in South Africa's open land rovers
empty sand bags for everywhere else
normal odds and ends
I normally split my gear between my carry-on and my personal bag and have never had any issues with any of the airlines I have used (South African can be a headache at times, though).
Give us more info and well return the favor, I think.
General answers to your questions, though, look like this: Your outfitter/guide will tell you what your weight load and equipment load should be, and what's acceptable to him. Some will be flexible for a price. Shipping to a fixed location in South or East Africa should be by DHL, will be VERY expensive, and should generally be aimed at arriving at your first destination, only if that is a private reserve. DHL can tell you specifically what the risks are for specific locations and destinations. Prices and insurance will vary quite a bit based on their risk factors.
You need to get an agenda planned asap and start talking to photo tour operators now if you want to go in 2018.
In South Africa and Namibia you do have an alternative of self driving in a rental vehicle (get a 4wd and stay away from all the major cities). I spent nearly 4 weeks with 3 other idiots in 2013 doing this in South Africa. Anyplace else you are most literally taking your life in your hands, especially Kenya at present.