Hey Jakezori, there are a lot of reasons not to mix lakes. The fish you listed as possible tank mates are carnivores, while most " assorted Africans " are Mbuna, which are vegetarians. This makes for problems because Mbuna will readily eat high protein foods suited for carnivores, and this often results in bloat on the part of your Africans.
Another problem is that fish from certain regions have their own ways of communicating. An act of appeasement from a New World cichlid often means " let's fight " to an African.
Some fish from different areas of the world can make for a nice community tank. Unfortunatley, this does not include cichlids for the most part.
I agree with Vader's point of view. Although I think a true biotope is very hard to pull off, making an effort to create an environment a fish is adapted to should be a main concern for all of us. Besides, not only will you have a great display, but you will also have an educational tool, as you have recreated a specific underwater environment in your own home.