A slight variation on the "African oddball" setup is very doable in a 100x40x50cm tank...
1/3x African Butterfly Fish
1/3x Leopard Bushfish
6-10x Yellow Tail Congo Tetra
6-10x Upside Down Synodontis (nigriventris)
The more you get of the predators, the less space you really have for the social tetras and catfish (you could possibly just about do both social species if you get singleton predators). Usually Congo Tetras are used, but they really need a longer tank, the Yellow Tails (Alestopetersius caudalis) will be fine providing you buy at least two females per male and ensure they are big enough not to be "live lunch" (so buy your tetras and catfish first and let them grow a bit before buying young bushfish and Butterfly Fish).
An alternative would be to do a small scale "Congo rapids" tank...
12-15x "Debauwi Catfish" (Pareutropius buffei or the smaller P. mandevillei that actually come from Malebo Pool, both enjoy current and must be kept in big groups)
2x Steatocranus sp. ultraslender (a small streamlined variant of the "Blockhead" Cichlid group, that is far more community friendly {although I have not seen how these behave when breeding})