When I went to Tanzania last year this is what I took:
A7R2 + laea3 + Tamron 150-600
A7R2 + 27-70 GM
A7R + 70-200
The A7R2 with 150-600 did most of the wildlife. The A7R2 with 24-70 did all the environmental and people shots. A7R with 70-200 saw the least usage. If I were to do it again, I could leave the A7R and 70-200 at home.
If you use e-mount, why not stick to it instead of learning the a mount? I don't see why you need both 70-400 and 150-600 unless you want one for backup. If it is reach you want w/ the A6500, the A7R2 cropped does about 18MP, not too far from the A6500 24MP
Don't forget the bean bags. And some insect repellents. The Tsetse flies are mean. Lots of SD cards and batteries in case you are unable to charge. Most places will have only one outlet, get a
portable power strip.