Kama nani?
There are thousands of FMCG. Out of this which particular ones would you think of manufacturing on that 50x100 you mentioned? Is this backed up by any form of market research?
Never worry about statistics. The only statistic that matters is if you own an apartment/house in or around Nairobi or not. If you own nothing in Nairobi then it does not matter if there is an oversupply or an undersupply, you are a mere spectator.