I'm going to play contrarian. If The United Party were in power, No Bantustans, but certainly power in White colored hands only. they would be more welcoming to Rhodesia. The Afrikaners run things at all costs idea wouldn't be there, and the Most manageable non white group, the colored would be coopted as in Sailsbury.Would need a less pragmatic, more extremist leadership than the apartheid state had in the 70s. Vorster in particular wanted peace in Rhodesia, with the option of a moderate black led government , more than trying to sustain a white state that was effectively radicalising the black opposition to it and risking a Frelimo lookalike on the Limpopo border.
Vorster would have intervened if something extreme happened eg ZANLA capturing FT Victoria, but he'd prefer peaceful coexistence that didn't threaten his state