So, no, Rhodesia can't be saved (and doesn't deserve to be) - not unless the landgrab of the early colonial period is butterflied away, or is less severe than in OTL.
As for greater black participation in the second worldQUOTE]
If the land grab did not happen, then the government would almost certainly go the way of every other country in Africa, and a conquering Rhodes namesake and traditions would go out the window.
As far as your opinion goes of deserving, well, history is not deserving, merely what power from the end of a gun and/or pen dictates it to be. I would greatly agree that participation in WWII is a big negative. Idi Amin was part of that post war, for instance, and others in the original fray. The biggest force for guerillas and political action were those blacks brought in from outside the country, due in part because they never went back to their hinterlands for a spell, unlike the local ones. Farther away one went from Harare (Salisbury pre 1979), the more the country language (first book published in the 1950's) fell away to no usefulness. Tribal issues became paramount. Local tribes near Salisbury/Harare could comute for a weekend easily and lost ties to local chiefs.
From those who have been in the area, with the UN for example, have told me that the movie The Air Up There 1994 does the most justice to the situation. One man tries to tie all the money down. Under that situation, no way would a Rhodesia stay Rhodesia.