Sounds like you have your mind made up, so you might not even bother reading this, but I must tell you that I did not meet a single pilot who was hired having spent less than 4 weeks in the country, with the exception of some from South Africa who came up for a few days, dropped of CVs, went home and came back a month or so later, or were called in SA.
So, since (and this is not racist, but political) Botswana and Namibia won't give more than 30 days visa to Indian citizens, there aren't many (if any) Indian nationals flying for charter operators in Bots or Nam. It's not that you get here, get hired and then can't get a visa (although that IS a problem for all pilots), but rather that you can't stay long enough for the operators to consider you.
Good luck.