I'd fly into Windhoek and rent a vehicle there - hire one with some decent clearance and traction at least, and if you are visiting the National Parks (e.g. Etosha in particular,) do not rent an open bakkie, er, pickup truck, as they are generally not allowed when the bed is exposed (not covered by a cap, etc.) iirc. Namibia isn't anywhere nearly as crowded for driving, and I'd think Capetown to Windhoek could be unnervingly tiring - and yes, there can be critters and other hard-to-see obstacles at night. At 100 kph, a kudu kud killya.