It would've been interesting if France had built more infrastructure in their colonies, like a rail network from Algiers/Tunis to Agadez/Niamey and then from there branches to Kano and Lagos in British Nigeria (maybe during WWI) and in French territory to Dakar.
Other interesting infrastructure would be dredging the Niger River to Niamey. It would be open for navigation to the sea for at least a few months (year round is unfeasible), and most of it would be done by Nigeria.
Makes me think the proposed Franco-British federation would've had an easier time developing their colonies.
Niger would probably be wealthier if it was part of a larger postcolonial French West African federation. The country was dealt a pretty bad hand at independence, most population centers are confined to a narrow band of arable land in the south of the country, and its main non-agricultural exports are natural resources like gold and uranium, creating a dutch disease effect that harms any emergent industrial sector.
Agreed, those larger federations would've been best for post-colonial Africa. It would also help Niger in particular if nuclear energy had been more heavily subsidized by governments since uranium has been an important export.
It should be part of a larger federation with Mali, Burkina Faso, and at least one coastal country like Benin, Togo, Guinea, or Ivory Coast for sea access. Severe climate change could make most of Niger uninhabitable as the Sahara creeps farther south every year, and Nigeriens become climate refugees in northern Nigeria.
Oddly, some models show slightly more rain in the Sahara. Not enough to green it, but it will slow desertification. That said, the solution is a well managed greenbelt which could provide food for livestock (and humans) as well as charcoal. This would take a bit of education on how to manage this since Ethiopia once imported mesquites for a similar purpose and they never really worked out but caused a lot of tension (although some herders got very rich off of the charcoal from them).
The entire Sahel region will face a conflict between herders moving south ahead of the desert that clash with farmers who already live there. The clash between farmers and pastoralists is a story that goes back to Cain and Abel.
This is ongoing, in Nigeria there's a lot of tension between the Fulani (mostly herdsmen) and other ethnic groups (mostly farmers) with violence on both sides. It doesn't help the Fulani have gained an association with Islamist terrorism amongst some Nigerians.