Well I thinks its a cool idea, just not practical at all. Now if your Bill Gates sure, but my sister and brother-in-law lived in Tanzania, and owned a bed and breakfast in South Africa, and from talking to them first hand I dont see your dream happening.
What I could see you doing is a going to say S. Africa and renting a Toyota and doing what you have planned to some extent, but bear in mind that those countrys are very very rural in most parts, little or no law enforcement also, with very very rugged terrain and if you break down nobodys coming to get you period.
Also Land Rovers, Toyotas, Nissan, Isuzu, Mistu. are far far more common than the Jeep, and most are diesel which is better b/c of the mileage and also the fuel over there isnt as clean and engine friendly as here, so diesel makes up for it, b/c its kinda a dirty fuel to start.
I once asked my brother-in-law about Land Rovers etc, and his resonse was I would take a Toyota landcrusier over any, I drove them over what are considered roads in Tanzania for 3 yrs, with nary a rattle or problem. Parts for the Toyotas are cheaper than the Land Rovers and sometimes it takes weeks, or even months to get a part if at all.
So in closing consider Mexico, closer, cheaper, and much more likely to happen, or think down under......good luck...and I hope you dont take this as me shooting down your dreams just trying to be helpful.