It is not up to the company to decide what and how people should eat. If cc want to bring their own food then let them. I fail to see how that is unsafe! Based on the quality of the food at some places it may in fact be preferable.
The per diem should cover reasonable food costs for a quality meal. To add to that the hotel should have 24 hour food service or be located in the city so that food can be obtained on OUR schedules which may differ widely from that of the local time.
What is unsafe is what is happening in Lagos - where the choice and timings are limited.