Oooh yes!
A Rooikat would be stunning!
I've attached a pic of a some Ratel IFV's crossing out of Angola over a bridge, which could look stunning in OFP.
Big thing IMHO would be the weapons, the SADF used the South African version of the Galil which we called the R-4, our helmets were of a similar shape as the US Army one's. Webbing was South African, however I would not quibble about using the US Style webbing, as in the early 80's we did wear something similar.
Anyway, such an addon would, I think, add to OFP's already awesome reputation, but then again I am biased
Cheers
Mech Etter